Methods of making an elastomer composite reinforced with silica and carbon black and products containing same

ABSTRACT

Methods to make a silica and carbon black elastomer composite with a destabilized dispersion that includes silica are described, along with particle reinforced elastomer composites made from the methods. The advantages achieved with the methods are further described.

The present invention relates to methods of making particle reinforcedelastomer composites. More particularly, the present invention relatesto a particle reinforced elastomer composite formed by a wet masterbatchmethod.

Numerous products of commercial significance are formed of elastomericcompositions wherein particulate reinforcing material is dispersed inany of various synthetic elastomers, natural rubber or elastomer blends.Carbon black and silica, for example, are widely used as reinforcingagents in natural rubber and other elastomers. It is common to produce amasterbatch, that is, a premixture of reinforcing material, elastomer,and various optional additives, such as extender oil. Numerous productsof commercial significance are formed of such elastomeric compositions.Such products include, for example, vehicle tires wherein differentelastomeric compositions may be used for the tread portion, sidewalls,wire skim and carcass. Other products include, for example, engine mountbushings, conveyor belts, windshield wipers, seals, liners, wheels,bumpers, and the like.

Good dispersion of particulate reinforcing agents in rubber compoundshas been recognized for some time as one of the most importantobjectives for achieving good quality and consistent productperformance, and considerable effort has been devoted to the developmentof methods to improve dispersion quality. Masterbatch and other mixingoperations have a direct impact on mixing efficiency and on dispersionquality. In general, for instance, when carbon black is employed toreinforce rubber, acceptable carbon black macro-dispersions can often beachieved in a dry-mixed masterbatch. However, high quality, uniformdispersion of silica by dry-mix processes poses difficulties, andvarious solutions have been offered by the industry to address thisproblem, such as precipitated silica in the form of “highly dispersiblesilica” or “HDS” flowable granules. More intensive mixing can improvesilica dispersion, but also can degrade the elastomer into which thefiller is being dispersed. This is especially problematic in the case ofnatural rubber, which is highly susceptible to mechanical/thermaldegradation.

In addition to dry mixing techniques, it is known to feed elastomerlatex or polymer solution and a carbon black or silica slurry to anagitated tank. Such “wet masterbatch” techniques can be used withnatural rubber latex and emulsified synthetic elastomers, such asstyrene butadiene rubber (SBR). However, while this wet technique hasshown promise when the filler is carbon black, this wet technique, whenthe filler is silica, poses challenges to achieving acceptable elastomercomposite. Specific techniques for producing wet masterbatch, such asthe one disclosed in U.S. Pat. No. 6,048,923, the contents of which areincorporated by reference herein, have not been effective for producingelastomer composites employing silica particles as the sole or principalreinforcing agent.

Accordingly, there is a need to improve methods that incorporate silicaand carbon black in elastomer composites in a wet masterbatch process,such as one that makes use of combining two fluids together undercontinuous, high energy impact conditions, so as to achieve anacceptable elastomer composite comprising silica particles as the soleor principal reinforcing agent.

SUMMARY OF THE PRESENT INVENTION

A feature of the present invention is to provide methods to produceelastomer composites using a wet masterbatch process which permits theuse of silica and carbon black, and yet achieves desirable particlereinforced elastomer composites.

To achieve these and other advantages, and in accordance with thepurposes of the present invention, as embodied and broadly describedherein, the present invention relates to the controlled and selectiveplacement or introduction of silica and carbon black in a wetmasterbatch process that forms a particle reinforced elastomercomposite.

The present invention further relates to a method of making an elastomercomposite in a wet masterbatch process that includes, but is not limitedto, the use of a fluid that includes an elastomer latex, and the use ofan additional fluid that includes a destabilized dispersion ofparticulate silica and carbon black. The ‘additional fluid’ is providedeither as i) two streams comprising a dispersion comprising carbon blackand a destabilized dispersion comprising silica; or ii) a single streamcomprising a dispersion comprising carbon black and a destabilizeddispersion comprising silica; or iii) a destabilized dispersioncomprising silica and carbon black. The two fluids are combined togetherunder continuous flow conditions and selected velocities. The combiningis such that the silica and carbon black are dispersed within theelastomer latex and, in parallel (or almost parallel), the elastomerlatex is transformed from a liquid to a solid or semi-solid elastomercomposite, such as to a solid or semi-solid silica-containing continuousrubber phase. This can occur, for instance, in about two seconds or lesssuch as a fraction of a second, due to the one fluid impacting the otherfluid with sufficient energy to cause the uniform and intimatedistribution of silica and carbon black particles in the elastomer. Theuse of a destabilized dispersion of silica in this masterbatch processenables formation of an elastomer composite with desirable properties.

The present invention further relates to elastomer composites formedfrom any one or more of the processes of the present invention. Thepresent invention also relates to articles that are made from or includethe elastomer composite(s) of the present invention.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are intended to provide a further explanation of the presentinvention as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this application, illustrate various features of the presentinvention and, together with the description, serve to explain theprinciples of the present invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A illustrates an exemplary mixing apparatus in accordance withProcess A-1;

FIG. 1B illustrates an exemplary mixing apparatus in accordance withProcess B;

FIG. 1C illustrates an exemplary mixing apparatus having an additionalinlet, in accordance with Process B; and

FIG. 2 is a block diagram of various steps that can occur in theformation of the elastomer composite according to embodiments of thepresent invention and in making rubber compounds with such elastomercomposites;

FIG. 3 is a block diagram of a process outlining the various steps thatcan occur in the formation of the dispersion containing the silica andcarbon black for use in the mixing apparatuses that can be used in thepresent invention;

FIG. 4 is a block diagram of another process outlining the various stepsthat can occur in the formation of the dispersion containing the silicaand carbon black for use in the mixing apparatuses that can be used inthe present invention;

FIG. 5 is a block diagram of another process outlining the various stepsthat can occur in the formation of the dispersion containing the silicaand carbon black for use in the mixing apparatuses that can be used inthe present invention;

FIG. 6 is a block diagram of another process outlining the various stepsthat can occur in the formation of the dispersion containing the silicaand carbon black for use in the mixing apparatuses that can be used inthe present invention; and

FIG. 7 is a block diagram of another process outlining the various stepsthat can occur in the formation of the dispersion containing the silicaand carbon black for use in the mixing apparatuses that can be used inthe present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The present invention relates to the selective and strategicintroduction of silica as well as carbon black into an elastomer latexin a continuous, rapid, wet masterbatch process. This process can becarried out in a semi-confined reaction zone, such as a tubular mixingchamber or other mixing chamber of an apparatus suitable for carryingout such a process under controlled volumetric flow and velocityparameters, leading to beneficial properties that would not be achieved,but for this selective and strategic use of especially silica. Asexplained in further detail herein, by ‘selective’, the presentinvention uses a destabilized dispersion of silica. And, by ‘strategic’introduction, the present invention uses at least two separate fluids,one fluid that includes an elastomer latex, and another fluid thatincludes the destabilized dispersion of silica and carbon black. The twofluids can be pumped or transferred into a reaction zone, such as asemi-confined reaction zone. The two fluids can be combined undercontinuous flow conditions, and under selected volumetric flow andvelocity conditions. The combining under pressure with selecteddifferential velocity conditions is sufficiently energetic that thesilica and carbon black can be distributed in two seconds or less, suchas in milliseconds, within the elastomer latex, and the elastomer latexis transformed from a liquid to a solid phase, such as to a particlereinforced elastomer composite in the form of a solid or semi-solidsilica and carbon black-containing continuous rubber phase.

The present invention relates in part, to a method of producing a silicaelastomer composite, comprising, consisting essentially of, consistingof, or including:

(a) providing a continuous flow under pressure of at least a first fluidcomprising a destabilized dispersion of particles (e.g., silica andcarbon black) and providing a continuous flow of a second fluidcomprising elastomer latex;

(b) adjusting volumetric flows of the first fluid and the second fluidto yield an elastomer composite having a silica content of from about 15phr to about 180 phr; and

(c) combining the first fluid flow and the second fluid flow (forinstance in a semi-confined reaction zone) with sufficient impact todistribute the silica and carbon black within the elastomer latex, toobtain a flow of a solid silica and carbon black-containing continuousrubber phase or semi-solid silica and carbon black-containing continuousrubber phase. The method transforms the elastomer latex from a liquid toa flow of a solid or semi-solid silica and carbon black-containingcontinuous rubber phase. The silica and carbon black-containingcontinuous rubber phase can be recovered as a substantially continuousflow of the solid or semi-solid silica and carbon black-containingcontinuous rubber phase. With regards to (a) the first fluid, the firstfluid can be provided either as i) two streams comprising a dispersioncomprising carbon black and a destabilized dispersion comprising silica;or ii) a single stream comprising a dispersion comprising carbon blackand a destabilized dispersion comprising silica; or iii) a destabilizeddispersion comprising silica and carbon black. Further details and/oroptions for the methods of the present invention are described below.Also, further variations of i), ii), and iii) are also provided below indetail.

As used herein, “silica” means particulate silicon dioxide, or aparticle coated with silicon dioxide, and includes precipitated silicain any form, such as highly dispersible (HDS) granules, non-HDSgranules, silica aggregates and silica particles; colloidal silica;fumed silica; and any combinations thereof. Such silicon dioxide orsilicon dioxide coated particles may have been chemically treated toinclude functional groups bonded (attached (e.g., chemically attached)or adhered (e.g., adsorbed)) to the silica surface. Thus, “silica”includes any particle having a surface substantially consisting ofsilica or silica having functional groups bonded or attached to it.

As used herein, “dispersion” means a stable suspension of solidparticles in aqueous fluid, wherein the charge at the surface of theparticles prevents particle agglomeration and the dispersion ischaracterized by a zeta potential magnitude of greater than or equal to30 mV.

Zeta potential is used to measure stability of charged particles, suchas silica particles, dispersed in a fluid. Measurement of zeta potentialcan have a variance of, for instance +/−2 mV, and, as used herein, zetapotential magnitude refers to the absolute value of the number, e.g., azeta potential value of minus 30 mV has a greater magnitude than a zetapotential value of minus 10 mV.

As used herein, “destabilized dispersion” means a suspension of solidparticles in an aqueous fluid wherein the charge at the surface of theparticles has been reduced by the presence of an agent, or by treatmentof the solid particles, and is characterized by a zeta potentialmagnitude of less than 30 mV, or more preferably a zeta potential ofless than 28 mV or less than 25 mV. The aqueous fluid can be water, awater miscible fluid (e.g., alcohol or ether), partially water misciblefluid, or a mixture of fluids that contains at least a water miscible orpartially water miscible fluid.

As used herein, the terms “silica slurry” and “dispersion” mean adispersion of silica (that may also include carbon black) in an aqueousfluid, wherein the charge at the surface of the silica prevents particleagglomeration and the dispersion is characterized by a zeta potentialvalue with a magnitude of at least 30 mV. A silica slurry or dispersionmay be destabilized by treatment with sufficient agent(s), or bytreatment of the silica, to reduce the charge on the surface of thesilica and the resulting destabilized silica slurry (or destabilizedsilica dispersion) is characterized by a zeta potential magnitude ofless than 30 mV.

As used herein, the terms “uniform” and “uniformly” are intended tomean, conventionally for those skilled in the art, that theconcentration of a component, for example, particulate filler, in anygiven fraction or percentage (e.g., 5%) of a volume is the same (e.g.,within 2%) as the concentration of that component in the total volume ofthe material in question, e.g., elastomer composite or dispersion. Thoseskilled in the art will be able to verify the statistical uniformity ofthe material, if required, by means of measurements of concentration ofthe component using several samples taken from various locations (forexample near the surface or deeper in the bulk).

As used herein, a “silica elastomer composite” means a masterbatch (apremixture of reinforcing material (that may include carbon black),elastomer, and various optional additives, such as extender oil) ofcoherent rubber comprising a reinforcing amount (e.g., about 15 phr toabout 180 phr) of dispersed silica. Silica elastomer composite cancontain optional, further components such as acid, salt, antioxidant,antidegradants, coupling agents, minor amounts (e.g., 10 wt % or less oftotal particulates) of other particulates, processing aids, and/orextender oil, or any combinations thereof.

As used herein, a “solid silica and carbon black-containing continuousrubber phase” or “particle containing continuous rubber phase” means acomposite having a continuous rubber phase and a uniformly dispersedphase of reinforcing particles (e.g., silica and carbon black) and, forinstance, up to 90%, by weight, aqueous fluid. The solid silica andcarbon black-containing continuous rubber phase may be in the form of acontinuous rope or worm. When compressed these articles release water.The solid silica and carbon black-containing continuous rubber phase cancontain optional, further components such as acid, salt, antioxidant,coupling agents, minor amounts of other particulates (e.g., 10 wt % orless of total particulates), and/or processing oil, or any combinationsthereof.

As used herein, a “semi-solid silica and carbon black-containingcontinuous rubber phase” means a composite with a paste-likeconsistency, having a silica and carbon black-containing, continuousrubber phase. The semi-solid product has a continuous phase of rubber,with entrapped silica and carbon black uniformly distributed throughoutthe rubber phase. The semi-solid silica and carbon black-containingcontinuous rubber phase remains coherent and expels water, whileretaining solids content, upon further handling in one or moresubsequent operations selected to develop the paste-like or gel-likematerial into a solid silica and carbon black-containing continuousrubber phase.

As used herein, a “coherent” material is material existing in asubstantially unitary form that has been created by the adhesion of manysmaller parts, such as an elastic, solid mass of rubber created by theadhesion of many small rubber particles to each other.

As used herein, a “continuous flow” is a steady or constant flow of afluid without interruption from a supply source (e.g., tank). But, it isto be understood that temporary interruptions (e.g., a second or a fewminutes) of flow would still be considered a continuous flow (e.g., forinstance, when switching supply from various supply holding areas, suchas tanks and the like, or interrupting flows to accommodate downstreamunit processes or maintenance of the equipment).

FIGS. 3 through 7 provide various examples of processes that can be usedto prepare a destabilized dispersion that contains silica along withcarbon black. These exemplified processes are not exhaustive of thevarious processes that can be implemented using the methods of thepresent invention. In FIG. 3, carbon black 300 (e.g., in pellet orparticulate form) is combined with a water or aqueous fluid 302 to forma carbon black slurry 306. The carbon black slurry can then be subjectedto one or more agitation and/or milling and/or grinding and/or othermechanical processing step(s), other non-mechanical processing steps asdenoted by box 310. The boxes designated by dashed lines in the figuresare optional steps or processes that can be used. Generally, with theone or more processing steps 310, a carbon black slurry 314 that is auniformly dispersed carbon black slurry that is substantially free oflarger agglomerated particles is obtained. Parallel with these steps,water or aqueous fluid 302, from the same source or different source asfor the carbon black, is combined with silica 304 to form a silicaslurry 308. The silica slurry can be subjected to various processingsteps such as milling, and/or agitation, and/or grinding, and/or othermechanical and/or non-mechanical processing step(s), as well as othersteps described herein to result in a destabilized dispersion thatcontains or includes silica. As disclosed herein, the additional step(s)312 can include the addition of at least one acid and/or salt to formthe destabilized silica dispersion 316. Then, the carbon black slurryand the destabilized silica slurry can be considered the “first fluid”for purposes of the present invention, but as shown in FIG. 3, slurriesare added as two separate streams to the reaction zone 103: one streamcontaining the dispersion comprising the carbon black and the otherstream containing the destabilized dispersion comprising silica. Themanner in which the two streams are introduced into the reaction zone103 can be with the same volumetric flow rates or different volumetricflow rates, and/or with the same or different parameters and/or the sameor different pressures. As shown in FIG. 3 and as described in thepresent application, the second fluid which comprises the elastomerlatex 105 is also introduced into the reaction zone 103.

As another option, as depicted in FIG. 4, a variation of the process ofFIG. 3 can be used. For purposes of the figures, the same referencenumbers denote the same description from FIG. 3 unless otherwiseindicated. As shown in FIG. 4, carbon black 300 is combined with wateror an aqueous fluid 302 to form a carbon black slurry 306. Further,water or an aqueous fluid 302 from the same or different source, iscombined with silica 304 to form a silica slurry 308. Further processingsteps for the carbon black can occur as depicted by box 310 and furtherprocessing of the silica slurry to result in a destabilized silicaslurry can occur as shown in box 312. Unlike FIG. 3, instead of usingtwo separate streams to introduce the carbon black slurry and the silicaslurry into the reaction zone 103, in one option, as shown in FIG. 4,the carbon black slurry and the destabilized dispersion comprisingsilica are combined prior to the reaction zone 103, so as to form asingle stream 318 which is identified as a mixed slurry (e.g., adestabilized particle dispersion) which is then introduced into thereaction zone 103.

In FIG. 5, an option is shown where carbon black 300 and water oraqueous fluid 302 are combined along with silica 304, all in a singletank 320 to form a slurry comprising carbon black and silica. The mixedslurry 320 can then optionally be subjected to further processing thatcan include milling, grinding, fluidizing, agitation, and/or otherprocessing steps to cause the destabilization of the slurry with thesilica present, such as the addition of at least one acid and/or salt.It is noted that since the mixed slurry includes carbon black, theamount of destabilization may be less than would be desired for adispersion that contains an equivalent quantity of silica without thecarbon black. The mixed slurry 324 (e.g., destabilized particledispersion) can then be introduced into the reaction zone 103.

In FIG. 6, carbon black 300 and silica 304 are combined to form a drymixture of the two components 326 and then this dry mixture 326 iscombined with water or aqueous fluid 350 to form a wet mixture 328,which then can be subjected to further processing steps 330, which wouldbe the same steps as in FIG. 5 for processing step 322. This then formsa mixed well dispersed slurry 332 (e.g., a destabilized particledispersion) which can then be introduced into the reaction zone 103.

In FIG. 7, silica 304 is combined with water or aqueous fluid 302 toform a silica slurry 308 which is then subjected to further processingsteps 312 as described in FIG. 3. This dispersion comprising silica 316(e.g., destabilized silica dispersion) can then be introduced into thereaction zone 103. Then, dry carbon black in particulate form can beinjected or otherwise introduced either into the dispersion comprisingthe silica 316 prior to its introduction into the reaction zone 103 orcan be separately introduced 338, e.g., carbon black fluidized in astream of air, into the reaction zone 103 while the destabilizeddispersion comprising silica 316 is introduced into the reaction zone103 or the carbon black can be introduced to the latex flow 340.

The weight ratio (or based on a total filler weight basis) of silica tocarbon for any of the processes of the present invention can be fromabout 45:55, or 50:50 (silica:carbon black) to less than 90:10, or89.9:10, or from 50:50 to 89:11, or from 60:40 to 85:15 or from 70:30 to80:20.

The elastomer composite can be produced in a continuous flow processinvolving a liquid mixture of elastomer latex and destabilizeddispersion of silica (that may include carbon black). Any device, orapparatus or system can be used, provided the device, apparatus, orsystem can be operated such that a liquid mixture of elastomer latex anda destabilized silica dispersion (that may include carbon black) can becombined under continuous flow conditions and under controlledvolumetric flow, pressure, and velocity conditions, including, but notlimited to, the apparatus shown in FIG. 1A, 1B, or 1C, or any type ofeductor or ejector, or any other device arranged to combine a continuousflow of at least two flows of liquid under controlled volumetric flow,pressure, and velocity conditions into and through a reaction zone. Theapparatus described in US20110021664, U.S. Pat. No. 6,048,923,WO2011034589, WO2011034587, US20140316058, and WO2014110499 (eachincorporated in their entirety by reference) can be used or adapted tothe processes herein as well. Also, ejectors and eductors or syphonssuch as water jet eductors or steam jet syphons can be used (e.g., onescommercially available from Schutte & Koerting, Trevose, Pa.).

The apparatus can include various supply tanks, pipes, valves, metersand pumps to control volumetric flow, pressure, and velocity. Further,as indicated at inlet (3) in FIGS. 1A, 1B, and 1C, various types andsizes of nozzles or other orifice size control elements (3 a) can beemployed to control the velocity of the silica slurry. The volumetricdimension of the reaction zone (13) can be selected to provide desiredvolumetric flows of the fluids and the elastomer composite. The inlet(11) supplying the elastomer latex to the reaction zone may be taperedto provide different volumetric flow rates and velocities. Devices mayinclude an inlet (11) of uniform diameter, without any taper at theorifice leading to the reaction zone.

In the method, a fluid that includes an elastomer latex and anadditional fluid that includes a destabilized dispersion of silica andcarbon black supplied as one stream or separate streams, for instance,as a jet under pressure are combined together under continuous flowconditions and under selected volumetric flow rates, pressure, andvelocities to rapidly and intimately mix the two fluids. The combining,for instance in a semi-confined space under pressure, is such that thesilica and carbon black are distributed throughout the elastomer latexand, in parallel, the elastomer latex is transformed from a liquid to asolid or semi-solid phase, i.e., a liquid to solid inversion, orcoagulation, of the latex occurs, capturing the distributed silica andcarbon black and water in the rubber and forming a solid or semi-solidsilica and carbon black-containing continuous rubber phase in acontinuous or semi-continuous flow out of the reaction zone (e.g., fromopening at outlet (7) in FIGS. 1A-1C)). At this point, the product canbe considered an elastomer composite of a continuous rubber phasecontaining silica particles, a silica-containing coherent rubber, or aparticle reinforced elastomer composite. It is believed that the silicaand carbon black particles first must be distributed in the elastomerlatex to obtain the desired product, and the liquid to solid phaseinversion follows immediately upon the silica and carbon blackdistribution. However, with the continuous and extremely rapid rate ofcombining the fluids (i.e., less than 2 seconds, less than 1 second,less than 0.5 second, less than 0.25 second, less than 0.1 second, or onthe order of milliseconds), and the energetic and intimate mixing ofrelatively small volumes of fluids in the reaction zone (e.g., fluidvolumes on the order of 10 to 500 cc), the parallel steps ofdistribution of the silica and carbon black particles and liquid tosolid phase transformation of the elastomer latex can happen nearlysimultaneously. The ‘reaction zone’ as used herein is the zone where theintimate mixing occurs along with coagulation of the mixture. Themixture moves through the reaction zone and to outlet (7).

An exemplary method for preparing the elastomer composite involvessimultaneously feeding a first fluid comprising a destabilizeddispersion of silica and carbon black (supplied as one stream or as twoseparate streams) and a second fluid comprising an elastomer latex (e.g.natural rubber latex) fluid to a reaction zone. The first fluidcomprising the destabilized dispersion of silica and carbon black can befed at a flow rate based on its volume, and the second fluid comprisingthe elastomer latex can be fed at a flow rate based on its volume (i.e.,volumetric flow rates). The volumetric flows of either the first fluid,the second fluid, or both the first and second fluid can be adjusted orprovided so as to yield an elastomer composite having a silica contentof from 15 to 180 parts per hundred weight rubber (phr) (e.g., from 35to 180 phr, from 20 phr to 150 phr, from 25 phr to 125 phr, from 25 phrto 100 phr, from 35 to 115 phr, or from 40 phr to 115 phr, or from 40phr to 90 phr and the like). The fluid that contains the destabilizeddispersion of particles (e.g. silica and carbon black) may be referredto as the first fluid in some embodiments herein. This fluid is aseparate fluid from the fluid containing the elastomer latex. Eitherfluid can be introduced through one inlet or injection point or throughmore than one inlet or injection point.

The volumetric flow ratio of the first fluid (fluid that contains atleast the destabilized silica dispersion and carbon black) to the secondfluid (latex fluid) can be adjusted to permit the desired elastomercomposite to form. Examples of such volumetric flow ratios include, butare not limited to, a volumetric ratio of from 0.4:1 (first fluid tosecond fluid) to 3.2:1; from 0.2:1 to 2:1 and the like. The volumetricflow ratio between the first fluid and second fluid can be adjusted byany means or technique. For instance, the volumetric flow rate of thefirst or second fluid or both can be adjusted by a) increasing thevolumetric flow rate, b) decreasing the volumetric flow rate, and/or c)adjusting the flow rates of the fluids relative to each other. Pressurecreated by physical constraints applied to the flow of the first fluidcauses formation of a high velocity jet that enables the combination ofthe destabilized silica dispersion with the elastomer latex to occurrapidly, e.g., in a fraction of a second. As an example, the time duringwhich two fluids are mixed and a liquid to solid phase inversion occurscan be on the order of milliseconds (e.g., about 50 ms to about 1500 msor about 100 ms to about 1000 ms). For a given selection of fluids, ifthe velocity of the first fluid is too slow to adequately mix thefluids, or the residence time is too short, then a solid rubber phaseand solid product flow may not develop. If the duration of the processis too long, back pressure may develop in the reaction zone and thecontinuous flow of materials halted. Likewise, if the velocity of thefirst fluid is too fast, and the duration of the process is too short, asolid rubber phase and solid product flow may not develop.

As described earlier, the relative volumetric flows of the first fluid(destabilized silica and carbon black slurry as a combined stream or astwo separate streams) and the second fluid (latex) can be adjusted, andwhen at least one salt is used as the destabilization agent, it ispreferred to adjust the volumetric flow ratio of destabilized particleslurry to elastomer latex so as to be 0.4:1 to 3.2:1. Other flow ratiosmay be used.

When at least one acid is used as the destabilization agent, it ispreferred to adjust the volumetric flow ratio of destabilized silicaslurry (or destabilized particle slurry) to elastomer latex so as to be0.2:1 to 2:1. Other flow ratios may be used.

The elastomer latex can contain at least one base (such as ammonia), andthe destabilized dispersion of silica (or destabilized particledispersion) can be achieved with the addition of at least one acid,wherein the molar ratio of the acid in the first fluid (silica) and thebase (e.g., ammonia) in the second fluid (latex) is at least 1.0, or atleast 1.1, or at least 1.2, such as from 1 to 2 or 1.5 to 4.5. The basecan be present in a variety of amounts in the elastomer latex, such as,but not limited to, 0.3 wt % to about 0.7 wt % (based on the totalweight of the elastomer latex), or other amounts below or above thisrange.

The destabilized particle dispersion as one stream or as two separatestreams, can be fed to the reaction zone preferably as a continuous,high velocity, e.g., about 6 m/s to about 250 m/s, or about 30 m/s toabout 200 m/s, or about 10 m/s to about 150 m/s, or about 6 m/s to about200 m/s, jet of injected fluid, and the fluid containing the elastomerlatex can be fed at a relatively lower velocity, e.g., about 0.4 m/s toabout 11 m/s, or about 0.4 m/s to about 5 m/s, or about 1.9 m/s to about11 m/s, or about 1 m/s to about 10 m/s or about 1 m/s to about 5 m/s.The velocities of the fluids are chosen for optimizing mixing betweenfluids and fast coagulation of elastomer latex. The velocity of theelastomer latex fed into the reaction zone should be preferably highenough to generate turbulent flow for better mixing with destabilizedparticle slurry. Yet, the velocity of the elastomer latex should be keptlow enough so that latex would not coagulate from shear before it iswell mixed with the destabilized particle slurry. In addition, thevelocity of the elastomer latex should be kept low enough before itenters into the reaction zone for preventing clogging of latex supplylines from coagulation of latex due to high shear. Similarly, there isalso an optimized range of the velocity of destabilized particledispersion. It is theorized that if the velocity of the destabilizedparticle slurry is too high, the rate of shear induced agglomeration ofsilica particles could be too high to allow adequate, uniform mixingbetween silica particles (and carbon black) and elastomer latexparticles.

While in this present invention, silica and carbon black are mixed withthe latex, the silica is generally the particle that requiresdestabilization in this process from the standpoint of achieving thedesirable solid or semi-solid continuous rubber phase. Thus, some of thediscussion here focuses on silica and its destabilization with therealization that this would apply equally to particle dispersions thatinclude not just silica but also carbon black.

Shear thickening from agglomeration and networking of silica particlesalso could reduce turbulence of the destabilized silica slurry andadversely affect the mixing between silica and latex. On the other hand,if the velocity of the destabilized silica slurry is too low, there maynot be sufficient mixing between silica particles and elastomer latexparticles. Preferably, at least one of the fluids entering into thereaction zone has a turbulent flow. In general, due to much higherviscosity of a typical destabilized silica dispersion relative to atypical elastomer latex, a much higher velocity of the destabilizedsilica dispersion is needed for generating good fluid dynamics formixing with the elastomer latex and fast coagulation of the latex. Suchhigh velocity flow of the destabilized silica dispersion may inducecavitation in the reaction zone to enhance rapid mixing of fluids anddistribution of silica particles in the elastomer latex. The velocity ofthe destabilized silica dispersion can be altered by using differentvolumetric flow rates, or a different nozzle or tip (3 a) (wider ornarrower in diameter) at the inlet (3) that feeds the first fluidcomprising destabilized silica dispersion. With use of a nozzle toincrease the velocity of the destabilized silica dispersion, it can beprovided under pressure ranging from about 30 psi to about 3,000 psi, orabout 30 psi to about 200 psi, or about 200 psi to about 3,000 psi, orabout 500 psi to about 2,000 psi or a relative pressure at least 2 timeshigher than the pressure applied to the fluid containing the elastomerlatex, or 2 to 100 times higher. The second fluid of elastomer latex canbe provided, as an example, at a pressure ranging from about 20 psi toabout 30 psi. The pressure in the first fluid supply system may be up toabout 500 psi.

Based on the production variables described herein, such as the velocityof the destabilized particle slurry fluid, the velocity of the latexfluid, the relative flow rates of the destabilized particle slurry andlatex fluids, the concentration of the destabilizing agent such as asalt and/or acid, the silica concentration in the destabilized slurry,the rubber weight percent in the latex, the ammonia concentration in thelatex, and/or the acid (if present) to ammonia ratio, it is possible tocontrol, obtain, and/or predict formation of a solid or semi-solidsilica-containing continuous rubber phase over a range of desired silicacontents. Thus, the process can be operated over an optimized range ofvariables. Thus, the a) velocity of one or both fluids, b) thevolumetric flow ratio of the fluids, c) the destabilized nature of thesilica, d) particulate silica concentration, e.g., 6 to 35 weightpercent, of the destabilized silica dispersion, and e) the dry rubbercontent, e.g., 10 to 70 weight percent, of the latex, can permit mixingunder high impact conditions so as to cause a liquid to solid inversionof the elastomer latex and uniformly disperse the silica in the latex ata selected silica to rubber ratio, and thus form a flow of a solid orsemi-solid silica-containing continuous rubber phase. The recovery ofthe flow of solid or semi-solid silica-containing continuous rubberphase can be achieved in any conventional technique for recovery of asolid or semi-solid flow of material. The recovery can permit the solidor semi-solid flow to enter into a container or tank or other holdingdevice. Such container or holding tank may contain a solution of salt oracid or both to effect further coagulation of the product to a moreelastic state. For example, the recovering can be transporting orpumping the solid flow to other processing areas or devices for furtherprocessing, of which some options are described herein. The recoveringcan be continuous, semi-continuous, or by batch. The outflow end of thereaction zone preferably is semi-confined and open to the atmosphere,and the flow of solid or semi-solid elastomer composite is preferablyrecovered at ambient pressure to allow continuous operation of theprocess.

The flow of a solid silica and carbon black-containing continuous rubberphase can be in the form of more or less elastic, rope-like “worms” orglobules. The solid silica and carbon black-containing continuous rubberphase may be capable of being stretched to 130-150% of its originallength without breaking. In other cases, a semi-solid silica and carbonblack-containing continuous rubber phase can be in the form ofnon-elastic, viscous paste or gel-like material that can develop elasticproperties. In each case, the output is a coherent, flowing solid whoseconsistency can be highly elastic or slightly elastic and viscous. Theoutput from the reaction zone can be a substantially constant flowconcurrent with the on-going feeding of the elastomer latex and thedestabilized dispersion of silica fluids into the reaction zone. Stepsin the process, such as the preparation of the fluids, may be done ascontinuous, semi-continuous, or batch operations. The resulting solid orsemi-solid silica and carbon black-containing continuous rubber phasecan be subjected to subsequent further processing steps, includingcontinuous, semi-continuous, or batch operations.

The solid or semi-solid silica and carbon black-containing continuousrubber phase created in the process contains water, or other aqueousfluid, and solutes from the original fluids, and, for instance, cancontain from about 40 wt % to about 95 wt % water, or 40 wt % to about90 wt % water, or from about 45 wt % to about 90 wt % water, or fromabout 50 to about 85 wt % water content, or from about 60 to about 80 wt% water, based on the total weight of the flow of particle reinforcedelastomer composite. As an option, after forming the solid or semi-solidsilica and carbon black-containing rubber phase comprising such watercontents, this product can be subjected to suitable de-watering andmasticating steps and compounding steps to develop desired rubberproperties and fabricate rubber compounds. Further details of theprocess and other post-processing steps are set forth below and can beused in any embodiment of the present invention.

A semi-solid silica and carbon black-containing continuous rubber phasemay be converted to a solid silica and carbon black-containingcontinuous rubber phase. This for instance can be done by subjecting thesemi-solid silica and carbon black-containing continuous rubber phase tomechanical steps that remove water from the composite and/or having thesemi-solid material sit for a time (e.g., after recovery from thereaction zone in an offline location) for instance, 10 minutes to 24hours or more; and/or heating the semi-solid silica and carbonblack-containing continuous rubber phase to remove water content (e.g.,a temperature of from about 50° C. to about 200° C.); and/or subjectingthe semi-solid material to acid or additional acid such as in an acidbath, or to salt or additional salt, or a salt bath, or to a combinationof acid and salt, and the like. One or more or all of these steps can beused. In fact, one or more or all of steps can be used as a furtherprocessing step(s) even when a solid silica and carbon black-containingcontinuous rubber phase is initially or subsequently recovered.

The degree of destabilization of the silica slurry, at least in part,determines the amount of silica that can be present in the silicaelastomer composite (e.g., captured and distributed uniformly within thecomposite) for a given silica concentration in the silica slurry and agiven dry rubber content of the latex. At lower selected target silicato rubber ratios (e.g., 15 phr to 45 phr), the concentration ofdestabilizing agent may not be high enough in the silica slurry andultimately the silica/latex mixture to rapidly coagulate and form asolid or semi-solid silica-containing continuous rubber phase. Inaddition, selecting appropriate silica and rubber concentrations andappropriate relative fluid flow rates as described herein areconsiderations for forming the solid or semi-solid product. For example,at relatively low volumetric flow ratios of destabilized slurry tolatex, the amount of the destabilizing agent in the destabilized silicaslurry may not be sufficient to facilitate rapid coagulation ofelastomer latex in the reaction zone. Generally, for a given elastomerlatex, lower silica loadings can be achieved by increasing thedestabilization of the silica slurry and/or reducing the weightpercentage of silica in the destabilized slurry.

When a dispersion of silica is destabilized, the silica particles tendto flocculate. When a dispersion of silica is too highly destabilized,the silica can ‘fall out’ of solution and become unsuited for use inpreferred embodiments.

When destabilization occurs, the surface charges on the silica aretypically not completely removed. However, sometimes when the silicaparticle, or the silica dispersion, is treated to destabilize, theisoelectric point (IEP) may be crossed over from a negative zetapotential to a positive zeta potential value. Generally for silica, thenet charge on the surface of the silica particles is reduced and themagnitude of the zeta potential is decreased during destabilization.

For higher silica to rubber ratios in the silica elastomer composite,one may select higher silica concentrations in the destabilized slurryand/or a higher silica fluid to latex fluid volumetric flow ratio. Oncethe silica slurry is destabilized and initially combined with the latexfluid, if the mixture does not coagulate, the volume flow ratio of thefirst fluid and second fluid can be adjusted, such as by decreasing thevolume flow of latex, which effectively provides a higher silica torubber ratio in the elastomer composite. In this step of adjusting theamount of latex present, the amount of latex is, or becomes, an amountthat does not cause excessive dilution of the concentration of thedestabilizing agent in the overall mixture such that the desired productcan be formed within the residence time in the reaction zone. To obtaina desired silica to rubber ratio in the elastomer composite, variousoptions are available. As an option, the level of destabilization of thesilica slurry can be increased, such as by reducing the magnitude of thezeta potential of the destabilized silica slurry (e.g., by adding moresalt and/or acid). Or, as an option, the silica concentration in thedestabilized silica slurry can be adjusted, for instance, by lowering orincreasing the silica concentration in the destabilized silica slurry.Or, as an option, a latex can be used that has a higher rubber content,or a latex can be diluted to a lower rubber content, or the relativeflow rate of the latex can be increased. Or, as an option, the flow rateand orifice size (where each can control or affect velocity of thefluid(s)) or relative orientation of the two fluid flows can be modifiedto shorten or lengthen the residence time of the combined fluids in thereaction zone, and/or alter the amount and type of turbulence at thepoint of impact of the first fluid on the second fluid. Any one or twoor more of these options can be used to adjust the process parametersand obtain a target or desired silica to rubber ratio in the elastomercomposite.

The amount or level of destabilization of the silica slurry is a majorfactor in determining what silica to rubber ratio can be achieved in thesilica elastomer composite. A destabilizing agent used to destabilizesilica in the slurry may play a role in accelerating coagulation ofelastomer latex particles when the destabilized silica slurry is mixedwith elastomer latex in the reaction zone. It is theorized that the rateof latex coagulation in the reaction zone may depend on theconcentration of the destabilizing agent in the combined fluids. It hasbeen observed that by running the process for producing silica elastomercomposite under various conditions, one may determine a thresholdconcentration of a destabilizing agent present in the combined mixtureof fluids at the time of mixing that is effective to produce solid orsemi-solid silica-containing continuous rubber phase. An example ofselecting and adjusting process conditions to achieve the thresholdconcentration to yield solid or semi-solid silica-containing continuousrubber phase, is described in the Examples below. If the thresholdconcentration for a given selection and composition of fluids,volumetric flows, and velocities is not equaled or exceeded, a solid orsemi-solid silica-containing continuous rubber phase will generally notbe produced.

The minimum amount of destabilization of the silica slurry (ordestabilization of the particle slurry) is indicated by a zeta potentialmagnitude of less than 30 mV (e.g. with zeta potentials such as −29.9 mVto about 29.9 mV, about −28 mV to about 20 mV, about −27 mV to about 10mV, about −27 mV to about 0 mV, about −25 mV to about 0 mV, about −20 mVto about 0 mV, about −15 mV to about 0 mV, about −10 mV to about 0 mVand the like). If the particle slurry has been destabilized to withinthis zeta potential range, then the silica in the destabilized slurrycan be incorporated into a solid or semi-solid silica-containingcontinuous rubber phase when combined with the elastomer latex.

While it may be desirable to destabilize the latex before combining itwith the silica containing slurry, under shear conditions such as thosepresent while continuously pumping the latex into the reaction zone, itis difficult to destabilize the latex fluid beforehand without causingpremature coagulation of the latex. However, the destabilization agentused in the destabilized silica slurry may be present in a surplusamount to enhance destabilization of the latex, and/or mitigate dilutionof the agent once the destabilized silica slurry and latex fluid arecombined. As a further option, at especially high silica concentrations(e.g., >25 wt % silica in the silica slurry), some added destabilizationagent can be added separately to the mixture of the destabilized silicaslurry and elastomer latex in the reaction zone to enhance coagulationof the latex.

Without wishing to be bound to any theory, the process for producingsilica elastomer composite is believed to form interpenetrated coherentnetworks of both rubber particles and silica aggregates in about twoseconds or less, such as a fraction of a second, as the two fluidscombine and the phase inversion occurs, resulting in a solid orsemi-solid material comprising these networks with encapsulated water.Such fast network formation allows the continuous production of a solidor semi-solid silica-containing continuous rubber phase. It is theorizedthat shear induced agglomeration of silica particles as the destabilizedsilica slurry passes through an inlet nozzle to be combined with theelastomer latex may be useful for creating unique, uniform particlearrangement in rubber masterbatches and capturing silica particleswithin rubber through hetero-coagulation between silica and rubberparticles. It is further theorized that without such an interpenetratednetwork, there may not be a composite of a solid or semi-sold,continuous rubber phase containing dispersed silica particles, in theshape of a worm, or solid pieces, for instance, that encapsulates 40-95wt % water and retains all or most of the silica in subsequentdewatering processes including squeezing and high energy mechanicalworking.

It is theorized that the formation of a silica network arises, at leastin part, from shear induced silica particle agglomeration as thedestabilized silica slurry passes through a pressurized nozzle (3 a) athigh velocity through the first inlet (3) into the reaction zone (13),as shown in FIGS. 1A-1C. This process is facilitated by reduction ofstability of silica in the destabilized slurry when the silica slurryhas been destabilized (e.g., by treating the silica slurry with salt oracid or both).

It is theorized that the liquid to solid phase inversion of the latexmay result from various factors, including shear induced coagulationfrom mixing with the high velocity jet of destabilized silica slurry,interaction of the silica surface with the latex components, ionic orchemical coagulation from contact with the silica slurry containingdestabilizing agent, and a combination of these factors. In order toform composite material comprising the interpenetrated silica networkand rubber network, the rates of each network formation as well as therate of mixing should be balanced. For example, for highly destabilizedsilica slurries at a high salt concentration in the slurry,agglomeration and network formation of silica particles occurs rapidlyunder shear conditions. In this case, volumetric flows and velocitiesare set so the latex has a rapid rate of coagulation for formation ofthe interpenetrated silica/rubber networks. Rates of formation areslower with more lightly destabilized silica slurries.

One exemplary process to produce a particle reinforced elastomercomposite includes feeding a continuous flow of a fluid that contains atleast elastomer latex (sometimes referred to as the second fluid)through inlet 11 (FIGS. 1A, 1B, and/or 1C), to a reaction zone 13 at avolumetric flow rate of about 20 L/hr to about 1900 L/hr. The methodfurther includes feeding a continuous flow of a further fluid containinga destabilized particle dispersion through inlet 3 (sometimes referredto as the first fluid) under pressure that can be accomplished by way ofnozzle tips (in FIGS. 1A-1C, at 3 a) at a volumetric flow rate of 30L/hr to 1700 L/hr. The destabilized state of the particle dispersion andthe impacting of the two fluid flows (introduced at inlets 3 and 11)under high energy conditions created by introducing the first fluid as ahigh velocity jet (e.g., about 6 m/s to about 250 m/s) that impacts thelower velocity latex flow (e.g., 0.4-11 m/s) entering the reaction zoneat an angle approximately perpendicular to the high speed jet of thefirst fluid is effective to intimately mix the particles (e.g., silicaand carbon black) with the latex flow, promoting a uniform distributionof particles in the flow of solid silica and carbon black-containingcontinuous rubber phase from the outlet of the reaction zone.

As an option, the elastomer latex introduced, for instance, throughinlet 11 can be a blend of two or more latexes, such as a blend of twoor more synthetic latexes. As an option, the devices in FIGS. 1A, 1B,and/or 1C can be modified to have one or more additional inlets so as tointroduce other components to the reaction zone, such as one or moreadditional latexes. For instance, in FIG. 1C, inlet 14 can be used tointroduce a further latex besides using inlet 11. The one or moreadditional inlets can be sequential to each other, or be adjacent toeach other or set forth in any orientation as long as the material (e.g.latex) being introduced through the inlet(s) has sufficient time todisperse or be incorporated into the resulting flow. In WO 2011/034587,incorporated in its entirety by reference herein, FIGS. 1, 2A, and 2Bprovide examples of additional inlets and their orientations which canbe adopted here for use with embodiments of the present invention. As aparticular example, one inlet can introduce a flow that includes naturalrubber latex and an additional inlet can introduce a synthetic elastomerlatex, and these latex flows are combined with the flow of thedestabilized dispersion of silica to result in the flow of a solid orsemi-solid silica-containing continuous rubber phase. When more than oneinlet is utilized for elastomer latex introduction, the flow rates canbe the same or different from each other.

FIG. 2 sets forth an example, using a block diagram of various stepsthat can occur in the formation of the elastomer composite. As shown inFIG. 2, the destabilized dispersion of particles that include silica(first fluid) 100 is introduced into the reaction zone 103 and the fluidcontaining the elastomer latex (second fluid) 105 is introduced alsointo the reaction zone 103. As an option, a flow of solid or semi-solidsilica and carbon black-containing continuous rubber phase exits thereaction zone 103 and can optionally enter a holding zone 116 (e.g., aholding tank, with or without the addition of a salt or acid solution tofurther enhance coagulation of rubber and formation of silica/rubbernetworks); and can optionally enter, directly, or after diversion to aholding zone 116, a dewatering zone 105; can optionally enter acontinuous mixer/compounder 107; can optionally enter a mill (e.g., openmill, also called a roll mill) 109; can be subjected to additional extramilling 111 (same or different conditions as mill 109) (such as same ordifferent energy input); can be subjected to optional mixing by mixer115, and/or can be granulated using a granulator 117, and then canoptionally be baled, using a baler 119, and can optionally be brokendown by use of an additional mixer 121.

With regard to the silica, one or more types of silica, or anycombination of silica(s), can be used in any embodiment of the presentinvention. The silica suitable for reinforcing elastomer composites canbe characterized by a surface area (BET) of about 20 m²/g to about 450m²/g; about 30 m²/g to about 450 m²/g; about 30 m²/g to about 400 m²/g;or about 60 m²/g to about 250 m²/g; and for heavy vehicle tire treads aBET surface area of about 60 m²/g to about 250 m²/g or for example fromabout 80 m²/g to about 200 m²/g. Highly dispersible precipitated silicacan be used as the filler in the present methods. Highly dispersibleprecipitated silica (“HDS”) is understood to mean any silica having asubstantial ability to dis-agglomerate and disperse in an elastomericmatrix. Such determinations may be observed in known manner by electronor optical microscopy on thin sections of elastomer composite. Examplesof commercial grades of HDS include, Perkasil® GT 3000GRAN silica fromWR Grace & Co, Ultrasil® 7000 silica from Evonik Industries, Zeosil®1165 MP and 1115 MP silica from Solvay S.A., Hi-Sil® EZ 160G silica fromPPG Industries, Inc., and Zeopol® 8741 or 8745 silica from JM HuberCorporation. Conventional non-HDS precipitated silica may be used aswell. Examples of commercial grades of conventional precipitated silicainclude, Perkasil® KS 408 silica from WR Grace & Co, Zeosil® 175GRsilica from Solvay S.A., Ultrasil® VN3 silica from Evonik Industries,Hi-Sil® 243 silica from PPG Industries, Inc. and the Hubersil® 161silica from JM Huber Corporation. Hydrophobic precipitated silica withsurface attached silane coupling agents may also be used. Examples ofcommercial grades of hydrophobic precipitated silica include Agilon®400,454, or 458 silica from PPG Industries, Inc. and Coupsil silicas fromEvonik Industries, for example Coupsil 6109 silica.

Typically the silica (e.g., silica particles) have a silica content ofat least 20 wt %, at least 25 wt %, at least 30 wt %, at least 35 wt %,at least 40 wt %, at least 50 wt %, at least 60 wt %, at least 70 wt %,at least 80 wt %, at least 90 wt %, or almost 100 wt % or 100 wt %, orfrom about 20 wt % to about 100 wt %, all based on the total weight ofthe particle. Any of the silica(s) can be chemically functionalized,such as to have attached or adsorbed chemical groups, such as attachedor adsorbed organic groups. Any combination of silica(s) can be used.The silica that forms the silica slurry and/or destabilized silicaslurry can be in part or entirely a silica having a hydrophobic surface,which can be a silica that is hydrophobic or a silica that becomeshydrophobic by rendering the surface of the silica hydrophobic bytreatment (e.g., chemical treatment). The hydrophobic surface may beobtained by chemically modifying the silica particle with hydrophobizingsilanes without ionic groups, e.g.,bis-triethoxysilylpropyltetrasulfide. Such a surface reaction on silicamay be carried out in a separate process step before dispersion, orperformed in-situ in a silica dispersion. The surface reaction reducessilanol density on the silica surface, thus reducing ionic chargedensity of the silica particle in the slurry. Suitable hydrophobicsurface-treated silica particles for use in dispersions may be obtainedfrom commercial sources, such as Agilon® 454 silica and Agilon® 400silica, from PPG Industries. Silica dispersions and destabilized silicadispersions may be made using silica particles having low surfacesilanol density. Such silica may be obtained through dehydroxylation attemperatures over 150° C. via, for example, a calcination process.

Any reinforcing or non-reinforcing grade of carbon black may be selectedto yield the desired property in the final rubber composition. Examplesof reinforcing grades are N110, N121, N220, N231, N234, N299, N326,N330, N339, N347, N351, N358, and N375. Examples of semi-reinforcinggrades are N539, N550, N650, N660, N683, N762, N765, N774, N787, and/orN990.

The carbon black can have any STSA such as ranging from 10 m²/g to 250m²/g, 11 m²/g to 250 m²/g, 20 m²/g to 250 m²/g or higher, for instance,at least 70 m²/g, such as from 70 m²/g to 250 m²/g, or 80 m²/g to 200m²/g or from 90 m²/g to 200 m²/g, or from 100 m²/g to 180 m²/g, from 110m²/g to 150 m²/g, from 120 m²/g to 150 m²/g and the like. As an option,the carbon black can have an Iodine Number (I₂ No) of from about 5 toabout 35 mg I₂/g carbon black (per ASTM D1510). The carbon black can bea furnace black or a carbon product containing silicon-containingspecies, and/or metal containing species and the like. The carbon blackcan be for purposes of the present invention, a multi-phase aggregatecomprising at least one carbon phase and at least one metal-containingspecies phase or silicon-containing species phase (also known assilicon-treated carbon black, such as ECOBLACK™ materials from CabotCorporation). As stated, the carbon black can be a rubber black, andespecially a reinforcing grade of carbon black or a semi-reinforcinggrade of carbon black. Iodine number (I₂ No.) is determined according toASTM Test Procedure D1510. STSA (statistical thickness surface area) isdetermined based on ASTM Test Procedure D-5816 (measured by nitrogenadsorption). OAN is determined based on ASTM D1765-10. Carbon blackssold under the Regal®, Black Pearls®, Spheron®, Sterling®, Emperor®,Monarch®, Shoblack™, and Vulcan® trademarks available from CabotCorporation, the Raven®, Statex®, Furnex®, and Neotex® trademarks andthe CD and HV lines available from Columbian Chemicals, and the Corax®,Durax®, Ecorax®, and Purex® trademarks and the CK line available fromEvonik (Degussa) Industries, and other fillers suitable for use inrubber or tire applications, may also be exploited for use with variousimplementations. Suitable chemically functionalized carbon blacksinclude those disclosed in WO 96/18688 and US2013/0165560, thedisclosures of which are hereby incorporated by reference. Mixtures ofany of these carbon blacks may be employed.

The carbon black can be an oxidized carbon black, such as pre-oxidizedusing an oxidizing agent. Oxidizing agents include, but are not limitedto, air, oxygen gas, ozone, NO₂ (including mixtures of NO₂ and air),peroxides such as hydrogen peroxide, persulfates, including sodium,potassium, or ammonium persulfate, hypohalites such a sodiumhypochlorite, halites, halates, or perhalates (such as sodium chlorite,sodium chlorate, or sodium perchlorate), oxidizing acids such a nitricacid, and transition metal containing oxidants, such as permanganatesalts, osmium tetroxide, chromium oxides, or ceric ammonium nitrate.Mixtures of oxidants may be used, particularly mixtures of gaseousoxidants such as oxygen and ozone. In addition, carbon blacks preparedusing other surface modification methods to introduce ionic or ionizablegroups onto a pigment surface, such as chlorination and sulfonation, mayalso be used. Processes that can be employed to generate pre-oxidizedcarbon blacks are known in the art and several types of oxidized carbonblack are commercially available.

Further, the silica slurry and/or destabilized silica slurry cancontain, as an option, a minor amount (10 wt % or less, based on a totalweight of particulate material) of any non-silica and non-carbon blackparticles, such as zinc oxide, or calcium carbonate, or otherparticulate materials useful in rubber compositions.

Silica may be dispersed in aqueous fluid according to any techniqueknown to those of skill in the art. A dispersion of particulate silicacan be subjected to mechanical processing, for instance, to reduceparticle size. This can be done prior to or during or afterdestabilizing of the dispersion and can contribute in a minor way ormajor way to the destabilizing of the dispersion. The mechanicalprocessing can comprise or include grinding, milling, comminution,bashing, or high shear fluid processing, or any combinations thereof.

For example, a silica slurry can be made by dispersing silica in a fluidby means of a grinding process. Such a grinding process reduces the sizeof most silica agglomerates (e.g. over 80% by volume) in the fluid tobelow 10 microns, and preferably below 1 micron, the typical size rangeof colloidal particles. The fluid may be water, an aqueous fluid, or anon-aqueous polar fluid. The slurry, for instance, may comprise fromabout 6 wt % to about 35 wt % silica-containing particles, based on theweight of the slurry. The size of silica particles may be determinedusing a light scattering technique. Such a slurry when made in waterusing silica particles having low residual salt content at a pH of 6-8,typically has a zeta potential magnitude higher than, or equal to, 30 mVand shows good stability against aggregation, gelling, and settlement ina storage tank with slow stirring (e.g. stirring speed below 60 RPM). Aswell-ground silica particles are generally stable in water at a pH ofaround 7 due to high negative charges on silica, very high shear isgenerally needed to overcome the repulsive energy barrier betweenparticles to induce particle agglomeration.

In an exemplary method employing silica, such as HDS granules, thesilica can be combined with water, and the resulting mixture is passedthrough a colloid mill, pipeline grinder, or the like to form adispersion fluid. This fluid is then passed to a homogenizer that morefinely disperses the filler in the carrier liquid to form the slurry.Exemplary homogenizers include, but are not limited to, theMicrofluidizer® system commercially available from MicrofluidicsInternational Corporation (Newton, Mass., USA). Also suitable arehomogenizers such as models MS18, MS45 and MC120, and serieshomogenizers available from the APV Homogenizer Division of APV Gaulin,Inc. (Wilmington, Mass., USA). Other suitable homogenizers arecommercially available and will be apparent to those skilled in the artgiven the benefit of the present disclosure. The optimal operatingpressure across a homogenizer may depend on the actual apparatus, thesilica type, and/or the silica content. As an example, a homogenizer maybe operated at a pressure of from about 10 psi to about 5000 psi orhigher, for example, from about 10 psi to about 1000 psi, about 1000 psito about 1700 psi, about 1700 psi to about 2200 psi, about 2200 psi toabout 2700 psi, about 2700 psi to about 3300 psi, about 3300 psi toabout 3800 psi, about 3800 psi to about 4300 psi, or about 4300 psi toabout 5000 psi. As indicated earlier, the dispersion of particulatesilica is destabilized before carrying out the masterbatch process, andthe dispersion can be destabilized by following one of the techniquesmentioned herein, before, during, or after any grinding or similarmechanical process.

Depending on the wet masterbatch method employed, a high silicaconcentration in slurry may be used to reduce the task of removingexcess water or other carrier. For the destabilized dispersion of silicaparticles, the liquid used can be water or other aqueous fluid or otherfluid. For the destabilized dispersion, from about 6 weight percent toabout 35 weight percent filler may be employed, for example, from about6 weight percent to about 9 weight percent, from about 9 weight percentto about 12 weight percent, from about 12 weight percent to about 16weight percent, from about 10 weight percent to about 28 weight percent,from about 16 weight percent to about 20 weight percent, from about 20weight percent to about 24 weight percent, from about 24 weight percentto about 28 weight percent, or from about 28 weight percent to about 30weight percent, based on the weight of the destabilized dispersion. Forthe destabilized dispersion, a higher silica concentration can havebenefits. For instance, silica concentration in the destabilized slurrycan be at least 10 weight percent or at least 15 weight percent, basedon the weight of the slurry (e.g., about 12 wt % to about 35 wt % orabout 15.1 wt % to about 35 wt %, or about 20 wt % to about 35 wt %),which can provide benefits such as, but not limited to, reducedwastewater, increased production rates, and/or reduction of theequipment size needed for the process. Those skilled in the art willrecognize, given the benefit of this disclosure, that the silicaconcentration (in weight percent) of the silica slurry (and in thedestabilized silica slurry) should be coordinated with other processvariables during the wet process to achieve a desired silica to rubberratio (in phr) in the ultimate product.

Details of a dispersion that includes silica are further describedbelow. In general, a dispersion can be a material comprising more thanone phase where at least one of the phases contains or includes orconsists of finely divided phase domains, optionally in the colloidalsize range, dispersed throughout a continuous phase. A dispersion orslurry that includes silica or silica dispersion can be prepared as astable suspension of particulate silica in aqueous fluid, wherein thecharge at the surface of the particles prevents particle agglomerationand the dispersion is characterized by a zeta potential magnitude ofgreater than or equal to 30 mV. In such dispersions, the silicaparticles remain in stable dispersion, and/or suspension, with respectto aggregation and coalescence, for instance, for at least 8 hours. Astable dispersion can be one where constant particle size is maintained,and wherein the particles do not settle or gel, or take a very long timeto settle appreciably in the presence of slow or periodic stirring, forexample, not settling appreciably after 8 hours, or 12 hours or 24hours, or 48 hours. For instance, for colloidal silica particles welldispersed in aqueous fluid, stability can generally be observed from apH of 8 to 10. Further, with slow stirring of the dispersion, the silicaparticles remain suspended in the fluid by means of particle surfacecharge, particle surface polarity, pH, selected particle concentration,particle surface treatment, and combinations thereof. The fluid may beor include water, an aqueous mixture, or a water miscible or partiallymiscible fluid, such as various alcohols, ethers, and other lowmolecular weight water-miscible solvents, preferably having C₁-C₅organic groups (e.g., ethanol, methanol, propanol, ethyl ether, acetone,and the like). As indicated above, the dispersion, for instance, maycomprise about 6 wt % to about 35 wt %, about 10 wt % to about 28 wt %,about 12 wt % to about 25 wt %, or about 15 wt % to about 30 wt %silica-containing particles, based on the weight of the dispersion.

A stable dispersion may be a colloidal dispersion. In general, acolloidal dispersion or colloid can be a substance where dispersedparticles are suspended throughout another substance. Thedispersed-phase particles have a diameter of from approximately about 1nanometer to about 1000 nanometers, and typically about 100 nanometersto about 500 nanometers. In a stable colloidal dispersion, particlesize, density, and concentration are such that gravity does not causeparticles to settle out of dispersion easily. Colloids with themagnitude of zeta potential of 30 mV or over are generally regarded asstable colloidal systems. Reduction of particle stability (e.g., silica)in a colloid or dispersion due to charge stabilization can be measuredby reduction of magnitude of zeta potential. Particle size may bemeasured by a light scattering method.

A destabilized silica dispersion or destabilized particle dispersion canbe understood to be a dispersion of silica in a fluid wherein weakenedparticle-to-particle repulsive forces allow clustering of particles andformation of a silica particle-to-particle network or gel once thedestabilized dispersion is subjected to an effective amount of shear. Incertain cases, mechanical shear may cause destabilization of silicadispersions and clustering of silica particles. The higher the degree ofdestabilization of silica slurry, the lower the shear needed foraggregation of particles, and the higher the rate of particleaggregation. For a destabilized dispersion, the dispersion can comprisefrom about 6 wt % to about 35 wt % particulate silica (based on theweight of the dispersion), e.g., from about 8 wt % to about 35 wt %,from about 10 wt % to about 28 wt %, from about 12 wt % to about 25 wt%, from about 15 wt % to about 30 wt %. The aqueous fluid in thedestabilized dispersion of silica particles may be or include water, anaqueous mixture, or a water miscible or partially miscible fluid, suchas various alcohols, ethers, and other low molecular weightwater-miscible solvents, preferably having C₁-C₅ organic groups (e.g.,ethanol, methanol, propanol, ethyl ether, acetone, and the like). Toform silica elastomer composites, the stability of silica particles in aslurry or dispersion is reduced (i.e., destabilized) by lowering theelectrostatic energy barrier between particles using an effective amountof a destabilizing agent such as acid or salt or both before the slurryis mixed with latex. A destabilizing agent may be selected for itscapacity to reduce repulsive charge interaction among particle surfacesthat prevent particles from agglomeration in the fluid.

A destabilized dispersion of silica or that includes silica may beobtained by lowering the pH of the dispersion of silica to close to theisoelectric point of the silica (around pH 2 for typical hydrophilicsilicas). For example, destabilizing silica can be achieved by addingacid to lower a pH of the dispersion of particulate silica to 2 to 4,thus reducing the magnitude of the zeta potential of the dispersion toless than 30 mV, such as below about 28 mV (e.g., zeta potentials ofmagnitude of about 18 mV to about 6 mV for formic acid as thedestabilization agent). The addition of acid and/or salt into silicaslurry can effectively reduce the stability of silica particlesdispersed in water. The acid or salt molar concentration is generallythe dominant factor that determines the zeta potential of thedestabilized silica slurry. In general, a sufficient amount of acid orsalt or both can be used to reduce the magnitude of the zeta potentialof the silica slurry to less than 30 mV, such as 28 mV or less,preferably 25 mV or less, for producing a semi-solid or solidsilica-containing continuous rubber phase.

The amount of acid used to destabilize the silica dispersion can be anamount to obtain a zeta potential magnitude in the destabilizeddispersion of less than 30 mV, such as 28 mV or less, or 25 mV or lower.The acid can be at least one organic or inorganic acid. The acid can beor include acetic acid, formic acid, citric acid, phosphoric acid, orsulfuric acid, or any combinations thereof. The acid can be or include aC₁ to C₄ alkyl containing acid. The acid can be or include one that hasa molecular weight or a weight average molecular weight below 200, suchas below 100 MW, or below 75 MW, or from about 25 MW to about 100 MW.The amount of acid can vary and depend on the silica dispersion beingdestabilized. The amount of acid can be, for instance, from about 0.8 wt% to about 7.5 wt %, for example, from about 1.5 wt % to about 7.5 wt %or more (based on the total weight of the fluid comprising thedispersion of silica). If an acid is the only destabilizing agent used,the amount of acid can be an amount that lowers the pH of the dispersionof silica by at least 2 pH units, or to at least a pH of 5 or lower, orthe pKa range of the acid or acids in use, so as to reduce chargeinteractions among particles.

A destabilized dispersion may be obtained by treating a dispersion thatincludes silica with a destabilizing agent comprising one or more saltsto alter slurry zeta potential to the range described above. The saltcan be or include at least one metal salt (e.g., from Group 1, 2, or 13metals). The salt can be or include a calcium salt, magnesium salt, oraluminum salt. Exemplary counterions include nitrate, acetate, sulfate,halogen ions such as chloride, bromide, iodine, and the like. The amountof salt can be, for instance, from about 0.2 wt % to about 2 wt % ormore, for example, from about 0.5 or 1 wt % to about 1.6 wt % (based onthe weight of the fluid comprising the destabilized dispersion ofsilica).

A combination of at least one salt and/or at least one acid can be usedto destabilize the dispersion that includes the silica.

When the destabilized dispersion that includes silica is achieved withthe addition of at least one salt, the salt concentration in thedestabilized dispersion can be from about 10 mM to about 160 mM, orother amounts above or below this range.

When the destabilized dispersion that includes silica is achieved withthe addition of at least one acid, the acid concentration in thedestabilized dispersion can be from about 200 mM to about 1000 mM, forexample, about 340 mM to about 1000 mM, or other amounts above or belowthis range.

A destabilized dispersion may be made using silica particles treated tocomprise an appropriate amount of surface functional groups carryingpositive charges so that the net charges on the silica surface arereduced sufficiently to decrease the magnitude of zeta potential of thedispersion below 30 mV. The net charge on the silica surface can bepositive, instead of negative, as a result of such surface treatment.The positively charged functional group may be introduced to silicasurface through chemical attachment or physical adsorption. For example,the silica surface may be treated withN-trimethoxylsilylpropyl-N,N,N-trimethylammonium chloride either beforeor after preparation of the silica dispersion. It is also possible toadsorb cationic coating agents, such as amine containing molecules andbasic amino acids on the silica surface. It is theorized that a netpositive charge on silica particle surfaces may enhance coagulation ofthe latex, which comprises negatively charged rubber particles, by meansof heterocoagulation.

With regard to the “second fluid,” which contains at least one elastomerlatex, this fluid may contain one or more elastomer latices. Anelastomer latex can be considered a stable colloidal dispersion ofrubber and may contain, for example, from about 10 wt % to about 70 wt %rubber based on the total weight of the latex. The rubber can bedispersed in a fluid, such as water or other aqueous fluid, for example.The aqueous content of this fluid (or water content) can be 40 wt % orhigher, such as 50 wt % or higher, or 60 wt % or higher, or 70 wt % orhigher, for instance from about 40 wt % to 90 wt % based on the weightof the fluid comprising the at least one elastomer latex. Suitableelastomer latices include both natural and synthetic elastomer laticesand latex blends. For example, elastomer latex may be made syntheticallyby polymerizing a monomer such as styrene that has been emulsified withsurfactants. The latex should be appropriate for the wet masterbatchprocess selected and the intended purpose or application of the finalrubber product. It will be within the ability of those skilled in theart to select suitable elastomer latex or a suitable blend of elastomerlatices for use in the methods and apparatus disclosed here, given thebenefit of this disclosure.

The elastomer latex can be or include natural rubber, such as anemulsion of natural rubber. Exemplary natural rubber latices include,but are not limited to, field latex, latex concentrate (produced, forexample, by evaporation, centrifugation or creaming), skim latex (e.g.,the supernatant remaining after production of latex concentrate bycentrifugation) and blends of any two or more of these in anyproportion. Natural rubber latex typically is treated with ammonia topreserve it, and the pH of treated latex typically ranges from 9 to 11.The ammonia content of the natural rubber latex may be adjusted, and canbe reduced, e.g., by bubbling nitrogen across or through the latex.Typically, latex suppliers desludge the latex by addition of diammoniumphosphate. They may also stabilize the latex by addition of ammoniumlaurate. The natural rubber latex may be diluted to a desired dry rubbercontent (DRC). Thus, the latex that can be used here can be a desludgedlatex. A secondary preservative, a mixture of tetramethylthiuramdisulfide and zinc oxide (TZ solution) may also be included. The latexshould be appropriate for the wet masterbatch process selected and theintended purpose or application of the final rubber product. The latexis provided typically in an aqueous carrier liquid (e.g., water). Theamount of the aqueous carrier liquid can vary, and for instance be fromabout 30 wt % to about 90 wt % based on the weight of the fluid. Inother words, such natural rubber latices may contain, or may be adjustedto contain, e.g., about 10 wt % to about 70 wt % rubber. Selection of asuitable latex or blend of latices will be well within the ability ofthose skilled in the art given the benefit of the present disclosure andthe knowledge of selection criteria generally well recognized in theindustry.

The natural rubber latex may also be chemically modified in some manner.For example, it may be treated to chemically or enzymatically modify orreduce various non-rubber components, or the rubber molecules themselvesmay be modified with various monomers or other chemical groups such aschlorine. Epoxidized natural rubber latex may be especially beneficialbecause the epoxidized rubber is believed to interact with the silicasurface (Martin, et al., Rubber Chemistry and Technology, May 2015,doi:10.5254/rct15.85940). Exemplary methods of chemically modifyingnatural rubber latex are described in European Patent Publications Nos.1489102, 1816144, and 1834980, Japanese Patent Publications Nos.2006152211, 2006152212, 2006169483, 2006183036, 2006213878, 2006213879,2007154089, and 2007154095, Great Britain Patent No. GB2113692, U.S.Pat. Nos. 6,841,606 and 7,312,271, and U.S. Patent Publication No.2005-0148723. Other methods known to those of skill in the art may beemployed as well.

Other exemplary elastomers include, but are not limited to, rubbers,polymers (e.g., homopolymers, copolymers and/or terpolymers) of1,3-butadiene, styrene, isoprene, isobutylene,2,3-dialkyl-1,3-butadiene, where alkyl may be methyl, ethyl, propyl,etc., acrylonitrile, ethylene, propylene and the like. The elastomer mayhave a glass transition temperature (Tg), as measured by differentialscanning calorimetry (DSC), ranging from about −120° C. to about 0° C.Examples include, but are not limited to, styrene-butadiene rubber(SBR), natural rubber and its derivatives such as chlorinated rubber,polybutadiene, polyisoprene, poly(styrene-co-butadiene) and the oilextended derivatives of any of them. Blends of any of the foregoing mayalso be used. The latex may be in an aqueous carrier liquid. Particularsuitable synthetic rubbers include: copolymers of styrene and butadienecomprising from about 10 percent by weight to about 70 percent by weightof styrene and from about 90 to about 30 percent by weight of butadienesuch as a copolymer of 19 parts styrene and 81 parts butadiene, acopolymer of 30 parts styrene and 70 parts butadiene, a copolymer of 43parts styrene and 57 parts butadiene and a copolymer of 50 parts styreneand 50 parts butadiene; polymers and copolymers of conjugated dienessuch as polybutadiene, polyisoprene, polychloroprene, and the like, andcopolymers of such conjugated dienes with an ethylenic group-containingmonomer copolymerizable therewith such as styrene, methyl styrene,chlorostyrene, acrylonitrile, 2-vinyl-pyridine,5-methyl-2-vinylpyridine, 5-ethyl-2-vinylpyridine,2-methyl-5-vinylpyridine, allyl-substituted acrylates, vinyl ketone,methyl isopropenyl ketone, methyl vinyl either, alpha-methylenecarboxylic acids and the esters and amides thereof, such as acrylic acidand dialkylacrylic acid amide. Also suitable for use herein arecopolymers of ethylene and other high alpha olefins such as propylene,1-butene, and 1-pentene. Blends of two or more types of elastomer latex,including blends of synthetic and natural rubber latex or with two ormore types of synthetic or natural rubber, may be used as well.

The rubber compositions can contain, in addition to the elastomer andfiller and coupling agent, various processing aids, oil extenders,antidegradants, antioxidants, and/or other additives.

The amount of silica (in parts per hundred of rubber, or phr) present inthe elastomer composite can be from about 15 phr to about 180 phr, about20 phr to about 150 phr, about 25 phr to about 80 phr, about 35 phr toabout 115 phr, about 35 phr to about 100 phr, about 40 phr to about 100phr, about 40 phr to about 90 phr, about 40 phr to about 80 phr, about29 phr to about 175 phr, about 40 phr to about 110 phr, about 50 phr toabout 175 phr, about 60 phr to about 175 phr, and the like.

The elastomer composite may optionally include an amount of carbon blackfor color, conductivity, and/or UV stability and/or for other purposes.

As indicated, the carbon black contained in the elastomer composite(reinforcing grades and non-reinforcing grades) can range, for instance,from greater than 10 wt % to about 55 wt %, or greater than 10 wt % toabout 50 wt %, or greater than 15 to about 40 wt %, based on the weightof the total particles present in the elastomer composite. Any grade ortype of carbon black(s) can be used, such as reinforcing, orsemi-reinforcing tire-grade furnace carbon blacks and the like.

In any method of producing an elastomer composite, the method canfurther include one or more of the following steps, after formation ofthe solid or semi-solid silica and carbon black-containing continuousrubber phase:

-   -   one or more holding steps or further solidification or        coagulation steps to develop further elasticity;    -   one or more dewatering steps can be used to de-water the        composite to obtain a dewatered composite;    -   one or more extruding steps;    -   one or more calendaring steps;    -   one or more milling steps to obtain a milled composite;    -   one or more granulating steps;    -   one or more baling steps to obtain a bailed product or mixture;    -   the baled mixture or product can be broken apart to form a        granulated mixture;    -   one or more mixing or compounding steps to obtain a compounded        composite.

As a further example, the following sequence of steps can occur and eachstep can be repeated any number of times (with the same or differentsettings), after formation of the solid or semi-solid silica and carbonblack-containing continuous rubber phase:

-   -   one or more holding steps or further coagulation steps to        develop further elasticity    -   dewatering the composite (e.g., the elastomer composite exiting        the reaction zone) to obtain a dewatered composite;    -   mixing or compounding the dewatered composite to obtain a        compounded mixture;    -   milling the compounded mixture to obtain a milled mixture (e.g.,        roll milling);    -   granulating or mixing the milled mixture;    -   optionally baling the mixture after the granulating or mixing to        obtain a baled mixture;    -   optionally breaking apart the baled mixture and mixing.

In any embodiment, a coupling agent can be introduced in any of thesteps (or in multiple steps or locations) as long as the coupling agenthas an opportunity to become dispersed in the elastomer composite.

As just one example, the solid or semi-solid silica and carbonblack-containing continuous rubber phase exiting the reaction zone orarea can be transferred by a suitable apparatus (e.g., belt orconveyor), to a dewatering extruder. Suitable dewatering extruders arewell known and commercially available from, for example, the French OilMill Machinery Co. (Piqua, Ohio, USA). Alternatively or in addition, thesolid or semi-solid silica and carbon black-containing continuous rubberphase may be compressed, for example, between metallic plates, to expelat least a portion of the aqueous fluid phase, e.g., to expel aqueousfluid until the water content of such material is below 40 wt %.

In general, the post processing steps can comprise compressing theelastomer composite to remove from about 1 wt % to about 15 wt % ormore, of an aqueous fluid phase, based on the total weight of theelastomer composite. The dewatering extruder may bring the elastomercomposite from, e.g., approximately about 40% to about 95% water contentto approximately about 5% to about 60% water content (for example, fromabout 5% to about 10% water content, from about 10% to about 20% watercontent, from about 15% to about 30% water content, or from about 30% toabout 50% water content) with all weight percent based on total weightof composite. The dewatering extruder can be used to reduce the watercontent of the elastomer composite to about 35 wt % or other amounts.The optimal water content may vary with the elastomer employed, theamount, and/or type of filler, and the devices employed for masticationof the dewatered product. The elastomer composite may be dewatered to adesired water content, following which the resulting dewatered productcan be further masticated while being dried to a desired moisture level(e.g., from about 0.5% to about 10%, for example, from about 0.5% toabout 1%, from about 1% to about 3%, about 3% to about 5%, or from about5% to about 10%, preferably below 1% all weight percent based on totalweight of product). The mechanical energy imparted to the material canprovide improvement in rubber properties. For example, the dewateredproduct may be mechanically worked with one or more of a continuousmixer, an internal mixer, a twin screw extruder, a single screwextruder, or a roll mill. This optional mixing step can have the abilityto masticate the mixture and/or generate surface area or expose surfacewhich can permit removal of water (at least a portion thereof) that maybe present in the mixture. Suitable masticating devices are well knownand commercially available, including for example, a Unimix ContinuousMixer and MVX (Mixing, Venting, eXtruding) Machine from FarrelCorporation of Ansonia, Conn., USA, a long continuous mixer from Pomini,Inc., a Pomini Continuous Mixer, twin rotor co-rotating intermeshingextruders, twin rotor counter-rotating non-intermeshing extruders,Banbury mixers, Brabender mixers, intermeshing-type internal mixers,kneading-type internal mixers, continuous compounding extruders, thebiaxial milling extruder produced by Kobe Steel, Ltd., and a KobeContinuous Mixer. Alternative masticating apparatus will be familiar tothose of skill in the art and can be used.

As dewatered product is processed in a desired apparatus, the apparatusimparts energy to the material. Without being bound by any particulartheory, it is believed that friction generated during mechanicalmastication heats the dewatered product. Some of this heat is dissipatedby heating and vaporizing the moisture in the dewatered product. Aportion of the water may also be removed by squeezing the material inparallel with heating. The temperature should be sufficiently high torapidly vaporize water to steam that is released to the atmosphereand/or is removed from the apparatus, but not so high as to scorch therubber. The dewatered product can achieve a temperature from about 130°C. to about 180° C., such as from about 140° C. to about 160° C.,especially when the coupling agent is added prior to or duringmastication. The coupling agent can include a small amount of sulfur,and the temperature should be maintained at a sufficiently low level toprevent the rubber from cross-linking during mastication.

As an option, additives can be combined with the dewatered product in amechanical mixer. Specifically, additives such as filler (which may bethe same as, or different from, the filler used in the mixer; exemplaryfillers include silica, carbon black, and/or zinc oxide), otherelastomers, other or additional masterbatch (i.e., the same or differentelastomer composite(s), comprising silica and/or carbon black),antioxidants, coupling agents, plasticizers, processing aids (e.g.,stearic acid, which can also be used as a curing agent, liquid polymers,oils, waxes, and the like), resins, flame-retardants, extender oils,and/or lubricants, and a mixture of any of them, can be added in amechanical mixer. Additional elastomers can be combined with thedewatered product to produce elastomer blends. Suitable elastomersinclude any of the elastomers employed in latex form in the mixingprocess described above and elastomers such as EPDM that are notavailable in latex form and may be the same or different than theelastomer in the silica-containing elastomer composite. Exemplaryelastomers include, but are not limited to, rubbers, polymers (e.g.,homopolymers, copolymers and/or terpolymers) of 1,3-butadiene, styrene,isoprene, isobutylene, 2,3-dialkyl-1,3-butadiene, where alkyl may bemethyl, ethyl, propyl, etc., acrylonitrile, ethylene, propylene, and thelike. Methods of producing masterbatch blends are disclosed in commonlyowned U.S. Pat. Nos. 7,105,595, 6,365,663, and 6,075,084 and PCTPublication WO2014/189826. The antioxidant (an example of a degradationinhibitor) can be an amine type antioxidant, phenol type antioxidant,imidazole type antioxidant, metal salt of carbamate, para-phenylenediamine(s) and/or dihydrotrimethylquinoline(s), polymerized quinineantioxidant, and/or wax and/or other antioxidants used in elastomerformulations. Specific examples include, but are not limited to,N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6-PPD, e.g.,ANTIGENE 6C, available from Sumitomo Chemical Co., Ltd. and NOCLAC 6C,available from Ouchi Shinko Chemical Industrial Co., Ltd.), “Ozonon” 6Cfrom Seiko Chemical Co., Ltd., polymerized 1,2-dihydro-2,2,4-trimethylquinoline (TMQ, e.g., Agerite Resin D, available from R. T. Vanderbilt),2,6-di-t-butyl-4-methylphenol (available as Vanox PC from VanderbiltChemicals LLC), butylhydroxytoluene (BHT), and butylhydroxyanisole(BHA), and the like. Other representative antioxidants may be, forexample, diphenyl-p-phenylenediamine and others such as, for example,those disclosed in The Vanderbilt Rubber Handbook (1978), pages 344-346.

The coupling agent can be or include one or more silane coupling agents,one or more zirconate coupling agents, one or more titanate couplingagents, one or more nitro coupling agents, or any combination thereof.The coupling agent can be or includebis(3-triethoxysilylpropyl)tetrasulfane (e.g., Si 69 from EvonikIndustries, Struktol SCA98 from Struktol Company),bis(3-triethoxysilylpropyl)disulfane (e.g., Si 75 and Si 266 from EvonikIndustries, Struktol SCA985 from Struktol Company),3-thiocyanatopropyl-triethoxy silane (e.g., Si 264 from EvonikIndustries), gamma-mercaptopropyl-trimethoxy silane (e.g., VP Si 163from Evonik Industries, Struktol SCA989 from Struktol Company),gamma-mercaptopropyl-triethoxy silane (e.g., VP Si 263 from EvonikIndustries), zirconium dineoalkanolatodi(3-mercapto) propionato-O,N,N′-bis(2-methyl-2-nitropropyl)-1,6-diaminohexane,S-(3-(triethoxysilyl)propyl) octanethioate (e.g., NXT coupling agentfrom Momentive, Friendly, W. Va.), and/or coupling agents that arechemically similar or that have the one or more of the same chemicalgroups. Additional specific examples of coupling agents, by commercialnames, include, but are not limited to, VP Si 363 from EvonikIndustries. It is to be appreciated that any combination of elastomers,additives, and additional masterbatch may be added to the dewateredproduct, for instance in a compounder.

As an option, the dewatered product can be masticated using an internalmixer such as a Banbury or Brabender mixer. The dewatered product mayfirst be brought to a moisture content of about 3 wt % to about 40 wt %,for example, about 5 wt % to about 20 wt %, or about 20 wt % to about 30wt %. The moisture content may be achieved by dewatering to the desiredlevel or by dewatering the dewatered product crumb to an intermediatemoisture content as the first step and then further reducing moisturecontent by heating the resulting dewatered product, or by letting waterevaporate from the dewatered product at room temperature, or by othermethods familiar to those of skill in the art. The dewatered product maythen be masticated in an internal mixer until a desired moisture levelor mechanical energy input is achieved. The dewatered product can bemasticated until it reaches a predetermined temperature, allowed tocool, and then placed back into the internal mixer one or more times toimpart additional energy to the material. Examples of temperaturesinclude from about 140° C. to about 180° C., for example, from about145° C. to about 160° C., or from about 150° C. to about 155° C. Thedewatered product may be sheeted in a roll mill after each masticationin the internal mixer. Alternatively or in addition, dewatered productthat has been masticated in a Banbury or Brabender mixer may be furthermasticated in an open mill.

As an option, the masticated product can be further processed on an openmill. The masticated product can be discharged from the continuouscompounder as a length of extrudate and may be cut into smaller lengthsprior to entering the open mill. The masticated product may optionallybe fed to the open mill via a conveyor. The conveyor may be a conveyorbelt, conduit, pipe, or other suitable means for transporting themasticated product from a continuous compounder to an open mill. Theopen mill can include a pair of rollers that may optionally be heated orcooled to provide enhanced operation of the open mill. Other operatingparameters of the open mill can include the gap distance between therolls, the bank height, i.e., the reservoir of material in the gapbetween and on top of the rolls, and the speed of each roll. The speedof each roll and the temperature of the fluid used to cool each roll maybe controlled independently for each roll. The gap distance may be fromabout 3 mm to about 10 mm or from about 6 mm to about 8 mm. The rollspeed may be about 15 rpm to about 70 rpm, and the rollers may rolltowards one another with respect to the inlet side of the mill. Thefriction ratio, the ratio of the speed of the collection roller, e.g.,the roller on which the masticated product collects, to that of the backroller, may be from about 0.9 to about 1.1. The fluid employed to coolthe rollers may be from about 35° C. to about 90° C., for example, fromabout 45° C. to about 60° C., from about 55° C. to about 75° C., or fromabout 70° C. to about 80° C. In addition to controlling the operation ofthe open mill to provide a desired level of mastication and desiccationto the masticated product, it is also desirable that the output of theopen mill should collect on the collection roller as a smooth sheet.Without being bound by any particular theory, it is thought that coolerroller temperatures facilitate this goal. The open mill may reduce thetemperature of the masticated product to approximately about 110° C. toabout 140° C. The residence time of the masticated product in the millcan be determined in part by the roller speed, the gap distance and theamount of mastication and drying desired and may be about 10 minutes toabout 20 minutes for material that has already been masticated, forexample, in a twin-rotor continuous mixer.

One skilled in the art will recognize that different combinations ofdevices may be employed to provide mastication and desiccation to asolid silica and carbon black-containing continuous rubber phaseproduced according to the various embodiments. Depending on whichdevices are used, it may be desirable to operate them under differentconditions than those described above to impart varying amounts of workand desiccation to the material. In addition, it may be desirable toemploy more than one particular kind of device, e.g., an open mill orinternal mixer, in series or to pass masticated product through a givendevice more than one time. For example, the masticated product may bepassed through an open mill two or three or more times or passed throughtwo or three or more open mills in series. In the latter case, it may bedesirable to operate each open mill under different operatingconditions, e.g., speed, temperature, different (e.g. higher) energyinput, etc. Masticated product can be passed through one, two, or threeopen mills after being masticated in an internal mixer.

The elastomer composite may be used to produce an elastomer or rubbercontaining product. As an option, the elastomer composite may be used inor produced for use in various parts of a tire, for example, tires, tiretreads, tire sidewalls, wire-skim for tires, and cushion gum for retreadtires. Alternatively or in addition, elastomer composite may be used forhoses, seals, gaskets, anti-vibration articles, tracks, track pads fortrack-propelled equipment such as bulldozers, etc., engine mounts,earthquake stabilizers, mining equipment such as screens, miningequipment linings, conveyor belts, chute liners, slurry pump liners, mudpump components such as impellers, valve seats, valve bodies, pistonhubs, piston rods, plungers, impellers for various applications such asmixing slurries and slurry pump impellers, grinding mill liners,cyclones and hydrocyclones, expansion joints, marine equipment such aslinings for pumps (e.g., dredge pumps and outboard motor pumps), hoses(e.g., dredging hoses and outboard motor hoses), and other marineequipment, shaft seals for marine, oil, aerospace, and otherapplications, propeller shafts, linings for piping to convey, e.g., oilsands and/or tar sands, and other applications where abrasion resistanceand/or enhanced dynamic properties are desired. The vulcanized elastomercomposite may be used in rollers, cams, shafts, pipes, tread bushingsfor vehicles, or other applications where abrasion resistance and/orenhanced dynamic properties are desired.

Traditional compounding techniques may be used to combine vulcanizationagents and other additives known in the art, including the additivesdiscussed above in connection with the dewatered product, with the driedelastomer composite, depending on the desired use.

The present invention further relates to an elastomer composite formedby any one or more methods described herein of the present invention.With the present invention, a solid silica and carbon black-containingrubber phase article can be produced and comprising at least 25 phrsilica (e.g., at least 29 phr, at least 35 phr, at least 40 phr silica)dispersed in rubber (such as natural rubber) and at least 40 wt %aqueous fluid and having a length dimension (L), wherein the solidsilica and carbon-containing continuous rubber phase article can bestretched to at least 130 to 150% of (L) without breaking. The solidsilica and carbon black-containing rubber phase article can have atleast 10 phr carbon black dispersed in the rubber (e.g., naturalrubber), such as at least 10 phr carbon black, at least 15 phr carbonblack, or at least 20 phr carbon black.

Unless otherwise specified, all material proportions described as apercent herein are in weight percent.

The present invention will be further clarified by the followingexamples which are intended to be only exemplary in nature.

EXAMPLES

In these examples, the “field latex” was field latex (Muhibbah LateksSdn Bhd, Malaysia) having a dry rubber content of about 30 wt %. The“latex concentrate” was latex concentrate (high ammonia grade, fromMuhibbah Lateks Sdn Bhd, Malaysia, or from Chemionics Corporation,Tallmadge, Ohio) diluted by about 50% to a dry rubber content of about30 wt % using either pure water or water with 0.6 wt % to 0.7 wt %ammonia. Unless noted otherwise, the “silica” was ZEOSIL® Z1165 MPprecipitated silica from Solvay USA Inc., Cranbury, N.J. (formerlyRhodia).

Thermogravimetric Analysis.

The actual silica loading levels were determined by thermogravimetricanalysis (TGA) following the ISO 6231 method.

Water Content of Product.

The test material was cut into mm size pieces and loaded into themoisture balance (e.g., Model MB35 and Model MB45; Ohaus Corporation,Parsippany N.J.) for measurement. The water content was measured at 130°C. for 20 minutes to 30 minutes until the test sample achieved aconsistent weight.

Slurry Zeta Potential.

In these examples, the zeta potential of particulate slurries wasmeasured using a ZetaProbe Analyzer™ from Colloidal Dynamics, LLC, PonteVedra Beach, Fla. USA. With multi-frequency electroacoustic technology,the ZetaProbe measures zeta potential directly at particleconcentrations as high as 60% by volume. The instrument was firstcalibrated using the KSiW calibration fluid provided by ColloidalDynamics (2.5 mS/cm). A 40 g sample was then placed into a 30 mL Tefloncup (Part #A80031) with a stir bar, and the cup was placed on a stirringbase (Part #A80051) with 250 rpm stirring speed. The measurement wasperformed using the dip probe 173 in a single-point mode with 5-pointrun at ambient temperature (approximately 25° C.). The data wereanalyzed using ZP version 2.14c Polar™ software provided by ColloidalDynamics. The zeta potential values can be negative or positivedepending on polarity of charge on the particles. The “magnitude” ofzeta potential refers to the absolute value (e.g., a zeta potentialvalue of −35 mV has a higher magnitude than a zeta potential value of−20 mV). The magnitude of the zeta potential reflects the degree ofelectrostatic repulsion between similarly charged particles indispersion. The higher the magnitude of zeta potential, the more stableof particles in dispersion. Zeta potential measurements were carried outon particulate silica slurries prepared as described below.

Dry silica was weighed and combined with deionized water using a5-gallon bucket and a high shear overhead laboratory mixer with ashrouded agitator (Silverson Model AX3, Silverson Machines, Inc., EastLongmeadow, Mass.; operating at 5200-5400 rpm for 30 minutes to 45minutes). Once the silica was roughly dispersed in water and able to bepumped, the silica slurry was transferred via a peristaltic pump(Masterflex 7592-20 system—drive and controller, 77601-10 pump headusing I/P 73 tubing; Cole-Palmer, Vernon Hills, Ill.) into a mixing loopwith an inline high shear rotor-stator mixer (Silverson Model 150LBlocated after the peristaltic pump, operated at 60 Hz) in a run tank (30gal. convex bottom port vessel) and was ground to further break downsilica agglomerates and any remaining silica granules. The slurry in therun tank was then circulated at 2 L/min using the same peristaltic pumpthrough the mixing loop for a time sufficient for turnover of at least5-7 times of the total slurry volume (>45 minutes) to make sure anysilica agglomerates were properly ground and distributed. An overheadmixer (Ika Eurostar power control visc-P7; IKA-Works, Inc., Wilmington,N.C.) with a low shear anchor blade rotating at about 60 rpm was used inthe run tank to prevent gelling or sedimentation of silica particles. Anacid (formic acid or acetic acid, reagent grade from Sigma Aldrich, St.Louis, Mo.) or salt (calcium nitrate, calcium chloride, calcium acetateor aluminum sulfate, reagent grade from Sigma Aldrich, St. Louis, Mo.)was added to the slurry in the run tank after grinding. The amount ofsilica in the slurry and the type and concentration of acid or salt areindicated in the specific Examples below.

Exemplary Process B.

Where indicated in the examples below, an exemplary method was carriedout utilizing Exemplary Process B. In Process B, dry silica was weighedand combined with deionized water using a 5-gallon bucket and a highshear overhead laboratory mixer with a shrouded agitator (SilversonModel AX3, Silverson Machines, Inc., East Longmeadow, Mass.; operatingat 5200 rpm to 5400 rpm for 30-45 minutes). Once the silica was roughlydispersed in water and able to be pumped, the silica slurry wastransferred via a peristaltic pump (Masterflex 7592-20 system—drive andcontroller, 77601-10 pump head using I/P 73 tubing; Cole-Palmer, VernonHills, Ill.) into a mixing loop with an inline high shear rotor-statormixer (Silverson Model 150LB located after the peristaltic pump,operated at 60 Hz) in a run tank (30 gal convex bottom port vessel) andwas ground to further break down silica agglomerates and any remaininggranules. The slurry in the run tank was then circulated at 2 L/minthrough the mixing loop for a time sufficient for turnover of at least5-7 times of the total slurry volume (>45 minutes) to make sure anysilica agglomerates were properly ground and dispersed. An overheadmixer (Ika Eurostar power control visc-P7; IKA-Works, Inc., Wilmington,N.C.) with a low shear anchor blade rotating at about 60 rpm was used inthe run tank to prevent gelling or sedimentation of silica particles. Anacid (formic acid or acetic acid, reagent grade from Sigma Aldrich, St.Louis, Mo.) or salt (calcium nitrate, calcium chloride, calcium acetate,or aluminum sulfate salt, reagent grade from Sigma Aldrich, St. Louis,Mo.) was added to the slurry in the run tank after grinding.

The latex was pumped using a peristaltic pump (Masterflex 7592-20system—drive and controller, 77601-10 pump head using I/P 73 tubing;Cole-Palmer, Vernon Hills, Ill.) through a second inlet (11) and into areaction zone (13) configured similarly to that shown in FIG. 1B. Thelatex flow rate was adjusted between about 25 kg/h to about 250 kg/h inorder to modify silica to rubber ratios of the elastomer composites.

When the silica was well dispersed in the water, the slurry was pumpedfrom the run tank through a diaphragm metering pump (LEWA-NikkisoAmerica, Inc., Holliston, Mass.) through a pulsation dampener (to reducepressure oscillation due to the diaphragm action) into either thereaction zone or the run tank via a recycle loop “T” connector. Thedirection of the slurry was controlled by two air actuated ball valves,one directing the slurry to the reaction zone and the other directingthe slurry to the run tank. When ready to mix the silica slurry withlatex, the line feeding the first inlet (3) to the reaction zone waspressurized to 100 psig to 150 psig by closing both valves. The ballvalve directing the slurry to the reaction zone was then opened andpressurized silica slurry was fed to a nozzle (0.020′ to 0.070″ ID) (3a) shown in FIG. 1B, at an initial pressure of 100 psig to 150 psig,such that the slurry was introduced as a high speed jet into thereaction zone. Upon contact with the latex in the reaction zone, the jetof silica slurry flowing at a velocity of 15 m/s to 80 m/s entrained thelatex flowing at 0.4 m/s to 5 m/s. In Examples according to embodimentsof the invention, the impact of the silica slurry on the latex caused anintimate mixing of silica particles with the rubber particles of thelatex, and the rubber was coagulated, transforming the silica slurry andthe latex into an elastomer composite comprising the silica particlesand 40 wt % to 95 wt % water trapped within a solid or semi-solidsilica-containing, continuous rubber phase. Adjustments were made to thesilica slurry flow rate (40 kg/hr to 80 kg/hr) or the latex flow rate(25 kg latex/hr to 300 kg latex/hr), or both, to modify silica to rubberratios (e.g., 15 phr to 180 phr silica) in the resulting product and toachieve the desired continuous production rates (30 kg/hr to 200 kg/hron dry material basis). Specific silica to rubber ratio (phr) contentsfollowing dewatering and drying are listed in the Examples below.

Process B Dewatering.

Material discharged from the reaction zone was recovered and sandwichedbetween two aluminum plates inside a catch pan. The “sandwich” was theninserted between two platens of a hydraulic press. With 2500 psigpressure exerted on the aluminum plates, water trapped inside the rubberproduct was squeezed out. If needed, the squeezed material was foldedinto a smaller piece and the squeezing process was repeated using thehydraulic press until the water content of the rubber product was below40 wt %.

Process B Drying and Cooling.

The dewatered product was put into a Brabender mixer (300 cc) for dryingand mastication to form a masticated, dewatered elastomer composite.Sufficient dewatered material was charged into the mixer to cover therotors. The initial temperature of the mixer was set at 100° C. and therotor speed was generally at 60 rpm. The water remaining in thedewatered product was converted to steam and evaporated out of the mixerduring the mixing process. As the material in the mixer expanded asresult of evaporation, any overflowing material was removed asnecessary. Either or both of a silane coupling agent (NXT silane,obtained from Momentive Performance Materials, Inc., Waterford, N.Y.; 8wt % silane on silica weight basis) and/or antioxidant (6-PPD,N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, Flexsys, St. Louis,Mo.) was optionally added to the mixer when the mixer temperature wasabove 140° C. When the temperature of the mixer reached 160° C., thematerial inside the mixer was held at 160° C. to 170° C. by varying therotor speed for 2 minutes before the material was dumped. Themasticated, dewatered elastomer composite was then processed on an openmill. The moisture content of the material being taken off of the milltypically was below 2 wt %.

Preparation of Rubber Compounds.

Dried elastomer composite obtained by Process B was compounded accordingto the formulation in Table A and the procedure outlined in Table B. Forsilica elastomer composites where either silane or antioxidant was addedduring drying, the final compound composition is as specified in TableA. The amount of silane coupling agent and/or antioxidant added duringcompounding was adjusted accordingly.

TABLE A Ingredient phr NR in Composite 100 Silica in Composite S 6PPD*(antioxidant) 2.0 Silane (NXT silane**) 0.08 × (phr silica) ZnO 4Stearic acid 2 DPG*** 1.5 Cure Rite ® BBTS**** 1.5 Sulfur 1.5*N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (Flexsys, St. Louis,MO) **main active component: S-(3-triethoxysilyl)propyl)octanethioate(Momentive, Friendly, WV) ***DiphenylGuanidine (Akrochem, Akron, OH)****N-tert-Butylbenzothiazole-2-sulphenamide (Emerald PerformanceMaterials, Cuyahoga Falls, OH) NR = natural rubber S = as stated

TABLE B Time (min) Operation Stage 1 Brabender mixer (300 cc), 65% fillfactor, 60 rpm, 100° C. 0 Add rubber-silica composite 1 Add silanecoupling agent, if needed Hold for 2 minutes beginning at 150° C. 2Sweep and add 6PPD and mix for 1 additional minute at 150° C. 3 SweepDump, 160° C. Pass through roll mill 6x Stage 2 Brabender mixer (300cc), 63% fill factor, 60 rpm, 100° C. 0 Add stage 1 compound 1 Add zincoxide and stearic acid 2 Sweep 4 Dump, 150° C. Pass through roll mill 6xStage 3 Brabender mixer (300 cc), 63% fill factor, 60 rpm, 100° C. 0 Addstage 2 compound, sulfur and accelerators 0.5 Sweep 1 Dump Roll mill forone minute with adequate band. Remove and perform 6 end rolls. Sheet offto required thickness.

Vulcanization was carried out in a heated press set at 150° C. for atime determined by a conventional rubber rheometer (i.e., T90+10% ofT90, where T90 is the time to achieve 90% vulcanization).

Properties of Rubber/Silica Compounds.

The tensile properties of vulcanized samples (T300 and T100, elongationat break, tensile strength) were measured according to ASTM standardD-412. Tan delta 60° was determined using a dynamic strain sweep intorsion between 0.01% and 60% at 10 Hz and 60° C. Tan δ_(max) was takenas the maximum value of tan δ₆₀ within this range of strains.

Example 1

A silica slurry with 27.8 wt % Zeosil® 1165 silica was prepared asdescribed above in connection with the Slurry Zeta Potential testmethod. The slurry was then diluted using either deionized water or asupernatant obtained from ultracentrifugation of the 27.8 wt % slurry tomake a series of silica slurries at various silica concentrations. Thezeta potential of various silica slurries was measured to show therelationship between the concentration of the silica in the slurry andthe zeta potential of the slurry. The zeta potential of the silicaslurry, as shown in Table 1, appears to depend upon the silicaconcentration when the silica slurry is made using deionized water.However, as shown in Table 2, when slurry was diluted using thesupernatant obtained from ultracentrifugation of the 27.8 wt % slurry,the zeta potential stays roughly the same at different silicaconcentrations.

TABLE 1 Zeta potential of slurry of silica made using deionized water.Silica Concentration in slurry (w/w) 6% 10% 15% 20% 22% 25% ZetaPotential (mV) −46.4 −42.7 −39.6 −36.2 −34.7 −32.3 pH 5.19 5.04 4.924.86 4.83 4.77

TABLE 2 Zeta potential of silica slurry made from dilution of a 27.8 wt% silica slurry using the supernatant of the 27.8 wt % silica slurry.Silica Concentration in slurry (w/w) 6% 22% Zeta Potential (mV) −31.5−31.4 pH 4.86 4.79

This result demonstrates that an increase of magnitude of zeta potentialwhen such silica slurries are diluted with deionized water is mostly dueto reduction of ionic strength of the slurry. The ions in the silicaslurry are believed to be from residual salts present in the silica fromthe silica particle manufacturing process. The high magnitude of zetapotential of the silica slurries (all over 30 mV) indicated that thesilica has high electrostatic stability in the slurry.

Example 2

The effect of adding salt or acid at various concentrations to silicaslurries on the zeta potential of these slurries is set forth in Table3. Slurries were prepared in deionized water by the Slurry ZetaPotential test method described above. Data summarized in Table 3illustrate the dependence of zeta potential of silica slurries anddestabilized silica slurries on the silica concentration, saltconcentration, and acid concentration. Adding salt or acid to silicaslurry reduces the magnitude of zeta potential, thus the stability ofthe silica slurry. As shown in Table 3, the zeta potential dependsmostly on the concentration of salt or acid in the slurry ordestabilized slurry, and not on silica concentration.

TABLE 3 Zeta potential of slurry and destabilized of silica at variousslurry concentrations, salt concentrations, and acid concentrations.Silica Concentration in Slurry (wt %) [acetic [formic [CaCl₂] acid]acid] Zeta (mM) (mM) (mM) (mV) pH 22.0 0 0 0 −34.4 4.80 6.0 0 0 0 −45.0ND 22.0 10.6 0 0 −24.2 4.49 22.0 29.7 0 0 −17.0 4.27 22.0 51.1 0 0 −14.64.17 22.0 105 0 0 −9.2 ND 22.0 155 0 0 −6.4 ND 6.0 4.6 0 0 −29.9 ND 6.010.4 0 0 −23.4 ND 6.0 27.6 0 0 −18.5 ND 6.0 46.4 0 0 −15.4 ND 6.0 140 00 −7.7 ND 22.0 0 98 0 −23.6 3.72 22.0 0 192 0 −21.4 3.65 22.0 0 564 0−17.1 3.26 22.0 0 1857 0 −12.7 ND 6.0 0 27 0 −33.6 3.84 6.0 0 45 0 −29.93.68 6.0 0 174 0 −22.1 3.38 6.0 0 431 0 −18.9 3.61 22.0 0 0 118 −15.33.17 22.0 0 0 197 −14.2 2.96 22.0 0 0 731 −10.7 2.46 22.0 0 0 1963 −6.52.04 6.0 0 0 36 −17.7 3.07 6.0 0 0 42 −17.4 3.04 6.0 0 0 168 −14.6 2.626.0 0 0 456 −11.4 2.29 22.0 10.7 0 130 −12.9 3.04 22.0 26.6 0 248 −9.02.78 22.0 101 0 978 −3.1 2.10 6.0 4.7 0 36 −15.9 3.12 6.0 46.4 0 224−10.1 2.41 ND = not determined.

Results shown in Table 3 illustrate the dependence of zeta potential ofsilica slurries and destabilized silica slurries on acetic acidconcentration and silica concentration. The data show that the zetapotential values are more dependent on the acid concentration than thesilica concentration. A similar relationship between zeta potential toacid concentration and silica concentration is observed for formic acid.At a given concentration, formic acid reduces zeta potential magnitudemore than acetic acid. As shown in Table 3, a combination of formic acidand calcium chloride was effective in reducing the zeta potentialmagnitude. The results in Table 3 show that the stability of silicaparticles in slurry can be reduced effectively through addition ofdestabilization agents, such as acid or salt or a combination of acidand salt. Similar results were seen for calcium nitrate and calciumacetate.

Example 3

In this example, the importance of destabilizing the dispersion ofsilica particles prior to contacting the silica dispersion withelastomer latex was established. Specifically, four experiments were runusing the mixing apparatus of FIG. 1C, equipped with three inlets (3,11, 14) for introducing up to three fluids into a confined reaction zone(13), such that one fluid impacted the other fluids at a 90 degree angleas a high speed jet at a velocity of 15 m/s to 80 m/s (See FIG. 1C). Inthree of the four experiments, the silica was ground as described abovein Process B and acetic acid was optionally added as described inExamples 3-A to 3-D, below. The slurry or destabilized slurry was thenpressurized to 100 psig to 150 psig and fed into the confined reactionzone through the inlet (3) at a volumetric flow rate of 60 liter perhour (L/hr) such that the slurry or destabilized slurry was introducedas a high speed jet at 80 m/s into the reaction zone. At the same time,natural rubber latex concentrate (60CX12021 latex, 31 wt % dry rubbercontent, from Chemionics Corporation, Tallmadge, Ohio, diluted withdeionized water) was introduced into the second inlet (11) through aperistaltic pump at a volumetric flow rate of 106 L/hr and velocity of1.8 m/s. These rates were selected and flows were adjusted to yield anelastomer composite product comprising 50 phr (parts per hundred weightdry rubber) silica. The silica slurry or destabilized silica slurry andlatex were mixed by combining the low velocity latex flow and the highvelocity jet of silica slurry or destabilized slurry through entrainingthe latex flow in the jet of silica slurry or destabilized silica slurryat the point of impact. The production rate (on a dry material basis)was set at 50 kg/hr. Specific actual silica to rubber ratios in rubbercomposites produced by the process are listed in the Examples below. TGAwas performed following drying according to the Process B method.

Example 3-A

First Fluid: A destabilized aqueous dispersion of 25 wt % of silica with6.2 wt % (or 1.18 M) acetic acid was prepared as described in Process Bdescribed above. The zeta potential of the destabilized slurry was −14mV, indicating that the slurry was significantly destabilized by theacid. The destabilized silica slurry was pumped continuously underpressure into the first inlet (3).

Second Fluid: Elastomer latex was supplied to the reaction zone throughthe second inlet (11).

The first fluid impacted the second fluid in the reaction zone.

Results: A liquid to solid phase inversion occurred in the reaction zonewhen the destabilized silica slurry and latex were intimately mixed byentraining the low velocity latex flow into the high velocity jet ofdestabilized silica slurry. During the entrainment process, the silicawas intimately distributed into the latex and the mixture coagulatedinto a solid phase which contained 70 wt % to 85 wt % of water. As aresult, a flow of a solid silica-containing, continuous rubber phase ina worm or rope-like shape was obtained at the outlet of the reactionzone (13). The composite was elastic and could be stretched to 130% ofthe original length without breaking. TGA analysis on the dried productshowed the elastomer composite contained 58 phr of silica.

Example 3-B

First Fluid: A destabilized aqueous dispersion of 25 wt % of silica with6.2 wt % acetic acid was prepared according to Process B describedabove. The zeta potential of the slurry was −14 mV, indicating theslurry was significantly destabilized by the acid. The destabilizedsilica slurry was pumped continuously under pressure into the firstinlet (3).

Second Fluid: Elastomer latex was supplied to the reaction zone throughthe second inlet (11).

Third Fluid: Deionized water was also injected into the reaction zonethrough third inlet (14) at a volumetric flow rate of 60 L/hr and avelocity of 1.0 m/s.

The three fluids met and impacted each other in the reaction zone.

Results: A liquid to solid phase inversion occurred in the reaction zoneand a solid or semi-solid silica containing continuous rubber phase in arope or worm-like shape was obtained from the outlet of the reactionzone. A significant amount of cloudy liquid containing silica and/orlatex flowed out of the outlet (7) with the solid or semi-solidsilica-containing continuous rubber phase. The silica-containingcontinuous rubber phase contained about 70 wt % to about 75 wt % waterbased on the weight of the composite. TGA analysis on the dried productshowed the elastomer composite contained 44 phr of silica. Thus, theaddition of water through the third inlet had a negative impact on theprocess, yielding a product with lower silica content (44 phr incontrast to 58 phr in Example 3-A) and significant waste product.

Example 3-C

First Fluid: A 10 wt % acetic acid aqueous solution without silica wasprepared. A continuous feed of the acid fluid was pumped using aperistaltic pump at a volumetric flow rate of 60 L/hr through the thirdinlet (14) into the reaction zone at a velocity of 1.0 m/s at the timeof entry into the reaction zone.

Second Fluid: Elastomer latex was supplied to the reaction zone throughthe second inlet (11) by a peristaltic pump at a velocity of 1.8 m/s anda volumetric flow rate of 106 L/hr.

The two fluids met and impacted each other in the reaction zone.

Results: A solid worm-like, sticky rubber phase was formed. TGA analysison the dried product showed the solid rubber phase contained no silica.

Example 3-D

First Fluid: An aqueous dispersion of 25 wt % of silica without aceticacid was prepared according to Process B described above. The silicaslurry was pumped under pressure continuously into the first inlet (3)at a volumetric flow rate of 60 L/hr and at a velocity of 80 m/s at thepoint of entry into the reaction zone. The zeta potential of the slurrywas −32 mV, indicating that silica was stably dispersed in the slurry.Thus, in this Example 3-D, the silica slurry was not destabilized byaddition of acid to the slurry prior to impacting the latex fluid.

Second Fluid: Elastomer latex was supplied to the reaction zone throughthe second inlet (11) by a peristaltic pump at a velocity of 1.8 m/s anda volumetric flow rate of 106 L/hr.

Third Fluid: After an initial period of continuous flow of the first andsecond fluids, a 10 wt % acetic acid aqueous solution was injectedthrough the third inlet (14) into the reaction zone at a volumetric flowrate that increased from 0 L/hr to 60 L/hr and a velocity that increasedfrom 0 m/s to 1.0 m/s. All three fluids impacted each other and mixed inthe reaction zone.

Results: Initially, prior to the injection of acid, no silica-containingcontinuous rubber phase formed and only cloudy liquid came out of thereaction zone outlet (7). Upon the injection of acid into the reactionzone (13), a worm-like, semi-solid silica-containing continuous rubberphase started to form as the flow of acetic acid through the third inletwas increased from 0 L/hr to 60 L/hr. The materials flowing from theoutlet still contained a significant amount of cloudy liquid, indicatinga significant amount of waste. TGA analysis of the dried product showedthat the silica-containing continuous rubber phase formed in thisexperimental run only contained 25 phr silica. Based on the productionconditions selected and the amount of silica used, if the silica hadbeen substantially incorporated into the silica-containing rubber phaseas in Example 3-A, the silica would have yielded a silica-containingrubber phase comprising in excess of 50 phr silica.

These experiments show that the silica slurry must be destabilized priorto initial impact with the elastomer latex in order to achieve thedesired silica-containing, continuous rubber phase. Example 3-A achievedwhat was considered efficient capture of the silica within the solidsilica-containing, continuous rubber phase, whereas Example 3-Dillustrates a comparative process utilizing an initially stable silicaslurry and demonstrating less than half of the efficiency of Example 3-Autilizing an initially destabilized silica slurry. The observation of acloudy liquid exiting the reaction zone exit point indicatesinsufficient mixing of the silica with the latex and a lower proportionof silica captured within the continuous rubber phase. It is theorizedthat in comparative processes 3B and 3D, there was insufficientdestabilization of fluids during mixing. The results further show thatpoor capture of silica occurs when additional fluid is added while thefirst fluid and second fluid are being mixed together, and such processconditions generate unwanted amounts of waste.

Example 4

Exemplary Process A-1. Where indicated in the examples below, a methodwas carried out utilizing Exemplary Process A-1. In Process A-1, dryprecipitated silica and water (municipal water filtered to removeparticulate matter) were metered and combined and then ground in arotor-stator mill to form a silica slurry, and the particulate slurrywas further ground in a feed tank using an agitator and anotherrotor-stator mill. The silica slurry was then transferred to a run tankequipped with two stirrers. The same process used to form the silicaslurry was used to prepare a carbon black slurry from dry carbon black(N-134 grade carbon black obtained from Cabot Corporation). The carbonblack slurry was added on top to the silica slurry in the run tank. Thesilica-carbon black slurry was recirculated from the run tank through ahomogenizer and back into the run tank. A solution of acid (formic acidor acetic acid, industrial grade obtained from Kong Long Huat Chemicals,Malaysia) was then pumped into the run tank. The slurry was maintainedin dispersed form through stirring and, optionally, by means of therecirculating loop in the run tank. After a suitable period, thesilica-carbon black slurry was fed to a confined reaction zone (13),such as the one shown in FIG. 1A, by means of the homogenizer. Theconcentration of silica and the carbon black in the slurry and theconcentration of acid are indicated in the specific Examples below.

The latex was pumped with a peristaltic pump (at less than about 40 psigpressure) through the second inlet (11) into the reaction zone (13). Thelatex flow rate was adjusted between about 300-1600 kg latex/hr in orderto obtain a desired production rate and silica-carbon black loadinglevels in the resulting product. The homogenized slurry containing acid,was pumped under pressure from the homogenizer to a nozzle(0.060″-0.130″ inside diameter (ID)) (3 a), represented by the firstinlet (3) shown in FIG. 1A, such that the slurry was introduced as ahigh speed jet into the reaction zone. Upon contact with the latex inthe reaction zone, the jet of silica slurry flowing at a velocity of 25m/s to 120 m/s entrained the latex flowing at 1 m/s to 11 m/s. InExamples according to embodiments of the invention, the impact of thesilica-carbon black slurry on the latex caused an intimate mixing ofsilica-carbon black particles with the rubber particles of the latex,and the rubber was coagulated, transforming the silica-carbon blackslurry and the latex into a material comprising a solid or semi-solidsilica-carbon black-containing continuous rubber phase containing 40 to95 wt % water, based on total weight of the material, trapped within thematerial. Adjustments were made to the slurry flow rate (500-1800kg/hr), or the latex flow rate (300-1800 kg/hr), or both, to modify thesilica to rubber ratios (e.g., 15-180 phr silica) in the final product,and to achieve the desired production rate. The production rates (drymaterial basis) were 200-800 kg/hr. Specific silica contents (by TGAanalysis) in the rubber following dewatering and drying of the materialare listed in the Examples below.

Process A-1 Dewatering.

Material was discharged from the reaction zone at atmospheric pressureat a flow rate from 200 to 800 kg/hr (dry weight) into a dewateringextruder (The French Oil Machinery Company, Piqua, Ohio). The extruder(8.5 inch I.D.) was equipped with a die plate with various die-holebuttons configurations and operated at a typical rotor speed of 90 to123 RPM, die plate pressure 400-1300 psig, and power of 80 kW to 125 kW.In the extruder, silica-carbon black-containing rubber was compressed,and the water squeezed out of the silica-containing rubber was ejectedthrough a slotted barrel of the extruder. Dewatered product typicallycontaining 15-60 wt % water was obtained at the outlet of the extruder.

Process A-1 Drying and Cooling.

The dewatered product was dropped into a continuous compounder (FarrelContinuous Mixer (FCM), Farrel Corporation, Ansonia, Conn.; with #7 and15 rotors) where it was dried, masticated and mixed with 1-2 phr ofantioxidant (e.g. 6PPD from Flexsys, St. Louis, Mo.) and optionallysilane coupling agent (e.g. NXT silane, obtained from MomentivePerformance Materials, Inc., Waterford, N.Y.; 8 wt % silane on silicaweight basis). The temperature of the FCM water jacket was set at 100°C., and the FCM temperature at the output orifice was 140° C. to 180° C.The moisture content of the masticated, dewatered elastomer compositeexiting the FCM was around 1 wt % to 5 wt %. The product was furthermasticated and cooled on an open mill. A rubber sheet of the elastomercomposite was directly cut from the open mill, rolled and cooled in air.

Preparation of Rubber Compounds.

Dried elastomer composite obtained by Process A-1 was compoundedaccording to the formulation in Table C and the procedure outlined inTable D. For elastomer composites where either silane or antioxidant wasadded during drying, the final compound composition is as specified inTable C. The amount of silane coupling agent and/or antioxidant addedduring compounding was adjusted accordingly.

TABLE C Ingredient phr NR in Composite 100 Carbon Black in Composite SSilica in Composite S 6PPD* (antioxidant) 2.0 Silane (NXT silane**) 0.08× (phr silica) ZnO 4 Stearic acid 2 DPG*** 1.5 Cure Rite ® BBTS**** 1.5Sulfur 1.5 *N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (Flexsys,St. Louis, MO) **main active component:S-(3-triethoxysilyl)propyl)octanethioate (Momentive, Friendly, WV)***DiphenylGuanidine (Akrochem, Akron, OH)****N-tert-Butylbenzothiazole-2-sulphenamide (Emerald PerformanceMaterials, Cuyahoga Falls, OH) NR = natural rubber S = as stated

TABLE D Time (min) Operation Stage 1 Brabender mixer (300 cc), 65% fillfactor, 60 rpm, 100° C. 0 Add rubber-silica-carbon black composite 1 Addsilane coupling agent, if needed Hold for 2 minutes beginning at 150° C.2 Sweep and add 6PPD and mix for 1 additional minute at 150° C. 3 SweepDump, 160° C. Pass through roll mill 6x Stage 2 Brabender mixer (300cc), 63% fill factor, 60 rpm, 100° C. 0 Add stage 1 compound 1 Add zincoxide and stearic acid 2 Sweep 4 Dump, 150° C. Pass through roll mill 6xStage 3 Brabender mixer (300 cc), 63% fill factor, 60 rpm, 100° C. 0 Addstage 2 compound, sulfur and accelerators 0.5 Sweep 1 Dump Roll mill forone minute with adequate band. Remove and perform 6 end rolls. Sheet offto required thickness.

Vulcanization was carried out in a heated press set at 150° C. for atime determined by a conventional rubber rheometer (i.e., T90+10% ofT90, where T90 is the time to achieve 90% vulcanization).

Properties of Rubber/Silica-Carbon Black Compounds.

The tensile properties of vulcanized samples (T300 and T100, elongationat break, tensile strength) were measured according to ASTM standardD-412. Tan delta 60° was determined using a dynamic strain sweep intorsion between 0.01% and 60% at 10 Hz and 60° C. Tan δ_(max) was takenas the maximum value of tan δ60 within this range of strains.

In these examples, the process according to various embodiments of theinvention was run in the apparatus shown in either FIG. 1A or 1B undervarious conditions as described in Table 4, utilizing Process A-1described above. Operating conditions were selected to yield a solid orsemi-solid silica-containing, continuous rubber phase with thesilica-carbon black to rubber ratios set forth in Table 4.

TABLE 4 Rubber Silica^(a) Carbon Content Salt concentration Black^(a) inLatex concentration Zeta in concentration Latex wt % in Potential Slurryin Slurry Latex (DRC) NH₃ Salt Slurry (Est.)^(b) Example (wt %) (wt %)Type (wt %) (wt %) Type (wt %) (mV) 4-1 15 1.5 Field 32.8 0.66 N/A 0.00−11.3 4-2 12.3 2.7 Field 32.8 0.66 N/A 0.00 −15.0 4-3 12.3 2.7 Field32.8 0.66 N/A 0.00 −15.0 4-4 12.3 2.7 Field 32.8 0.66 N/A 0.00 −15.0 4-512.3 2.7 Field 32.8 0.66 N/A 0.00 −15.0 4-6 12.3 2.7 Field 32.8 0.66 N/A0.00 −15.0 4-7 12.3 2.7 Field 32.8 0.66 N/A 0.00 −15.0 4-8 12.3 2.7Field 32.8 0.66 N/A 0.00 −15.0 4-9 12.3 2.7 Field 32.8 0.66 N/A 0.00−15.0 Actual Acid Inlet Actual Carbon Slurry Latex Slurry-to-Latex wt %in Acid/NH₃ Nozzle Silica Black Flow Flow Flow Acid Slurry molarVelocity^(c) loading loading Rate^(d) Rate^(d) Ratio Example Type (wt %)ratio (m/s) (phr) (phr) (L/hr) (L/hr) (v/v) 4-1 Formic 2.00 1.59 41 44 6800 626 1.278 4-2 Acetic 5.07 4.64 42 44 15 800 411 1.947 4-3 Acetic5.07 4.64 42 44 15 800 411 1.947 4-4 Acetic 5.07 3.77 42 34.2 13.5 800506 1.582 4-5 Acetic 5.07 3.77 65 30.4 10.6 800 506 1.582 4-6 Acetic5.07 4.64 65 37 14.6 800 411 1.947 4-7 Acetic 5.07 4.64 42 29.5 9.1 800411 1.947 4-8 Acetic 5.07 4.64 42 44.2 13.8 800 411 1.947 4-9 Acetic5.07 4.64 42 43.6 13.6 800 411 1.947 N/A = not applicable, ND = Notdetermined ^(a)All examples used ZEOSIL ® Z1165 MP precipitated silica.All Examples used N134 carbon black from Cabot Corporation. ^(b)Zetapotential values were estimated by interpolation of experimentallydetermined curves of zeta potential dependence on concentration of thesalt or the acid of the slurries of the same grade of silica. ^(c)Theinlet nozzle velocity is the velocity of the silica-carbon black slurryas it passes through a nozzle (3a) at first inlet (3) to the reactionzone (13) prior to contacting the latex. ^(d)Slurry and Latex Flow Ratesare the volumetric flow rates in L/hour of the silica-carbon blackslurry and the latex fluid, respectively, as they are delivered to thereaction zone.

In all the examples above in Table 4, the selected operating conditionsyielded a solid silica carbon black-containing, continuous rubber phasein a roughly cylindrical form. The product contained a major amount ofwater, was elastic and compressible, and expelled water and retainedsolids content when manually compressed. The solid material could bestretched, for example, the material could be stretched or elongated to130-150% of its original length, without breaking. Some of the rubberproperties of the composites made are shown in Table 5 below. Silica andcarbon black particles were observed to be uniformly distributedthroughout a continuous rubber phase and this product was substantiallydevoid of free silica particles and larger silica grains, both onexterior and interior surfaces. For the silica-carbon black-containing,continuous rubber phase to form, not only did the silica need to bedestabilized (e.g., by prior treatment with acids and/or salts), but thevolumetric flow rates of destabilized silica slurry relative to thelatex had to be adjusted not only for achieving a desired silica torubber ratio (phr) in the elastomer composite, but also for balancingthe degree of slurry destabilization to the rate of slurry and latexmixing and the rate of coagulation of latex rubber particles. By meansof such adjustments, as the silica slurry entrained the latex,intimately distributing silica particles (and carbon black particles)into the rubber, the rubber in the latex became a solid or semi-solidcontinuous phase, all within a fraction of a second after combining thefluids in the confined volume of the reaction zone. Thus, the processformed unique silica-carbon black elastomer composites by means of acontinuous fluid impact step done with sufficient velocity, selectedfluid solids concentrations and volumes, and adjusted fluid flow ratesto uniformly and intimately distribute the fine particulate silicawithin the latex and, in parallel, as such distribution occurs, to causea liquid to solid phase inversion of the rubber.

TABLE 5 Elongation @ Break (%) Tensile * Tensile Example Tan delta @Strength Strength Number T300/T100 60° C. (MPa) (MPa) 4-1 5.19 0.08932.20 535 4-2 4.98 0.113 29.31 463 4-3 4.99 0.106 29.74 455 4-4 5.780.084 34.72 529 4-5 5.60 0.093 31.37 468 4-6 5.35 0.110 31.86 504 4-74.86 0.127 29.64 448 4-8 4.85 0.123 29.45 446 4-9 4.48 0.118 29.61 457

The elastomer composite formed from these Examples had acceptable rubberproperties and especially showed beneficial T300/T100 properties for acomposite having silica and carbon black dispersed in the composite. Asshown in these examples, a solid silica and carbon black-containingrubber phase article can comprise at least 40 phr silica dispersed innatural rubber and at least 40 wt % aqueous fluid and can have a lengthdimension (L), wherein the solid silica and carbon black-containingcontinuous rubber phase article can be stretched to at least 130% to150% of (L) without breaking.

The present invention includes the followingaspects/embodiments/features in any order and/or in any combination:

1. A method of producing a silica elastomer composite, comprising:

(a) providing a continuous flow under pressure of at least one firstfluid containing dispersed particles and comprising a destabilizeddispersion of silica, and a continuous flow of at least a second fluidcomprising elastomer latex;

(b) providing volumetric flow of the first fluid relative to that of thesecond fluid to yield a silica content of about 15 phr to about 180 phrin the silica elastomer composite;

(c) combining the first fluid flow and the second fluid flow with asufficiently energetic impact to distribute the silica within theelastomer latex to obtain a flow of a solid silica-containing continuousrubber phase or semi-solid silica-containing continuous rubber phase,

wherein said at least one first fluid is provided as:

i) two streams comprising a dispersion comprising carbon black and adestabilized dispersion comprising silica; or

ii) a single stream comprising a dispersion comprising carbon black anda destabilized dispersion comprising silica; or

iii) a single stream of destabilized dispersion comprising silica andcarbon black.

2. The method of any preceding or following embodiment/feature/aspect,wherein said at least one first fluid is a destabilized dispersioncomprising silica and carbon black, and said method further comprisescombining dry carbon black, dry silica, and an aqueous medium to formsaid destabilized dispersion comprising at least 45 wt % silica, on atotal particle basis, and carbon black.3. The method of any preceding or following embodiment/feature/aspect,further comprising, subjecting one or more said dispersion(s) to atleast one mechanical processing step.4. The method of any preceding or following embodiment/feature/aspect,wherein said mechanical processing step comprises grinding, milling,comminution, bashing, or high shear fluid processing, or anycombinations thereof.5. The method of any preceding or following embodiment/feature/aspect,wherein said mechanical processing step comprises grinding saiddispersion(s) one or more times.6. The method of any preceding or following embodiment/feature/aspect,wherein said mechanical processing step reduces particle agglomeration,and/or adjusts particle size distribution.7. A method of producing a silica elastomer composite, comprising:

(a) providing a continuous flow under pressure of at least a first fluidcomprising a destabilized dispersion of silica and a continuous flow ofat least a second fluid comprising elastomer latex;

(b) providing volumetric flow of the first fluid relative to that of thesecond fluid to yield a silica content of about 15 phr to about 180 phrin the silica elastomer composite;

(c) providing a continuous flow of fluidized carbon black in dry form,

(d) combining the first fluid flow and the second fluid flow, and saidcarbon black with a sufficiently energetic impact to distribute thesilica and carbon black within the elastomer latex to obtain a flow of asolid silica-carbon black-containing continuous rubber phase orsemi-solid silica-carbon black-containing continuous rubber phase,

wherein said flow of carbon black is combined with said first fluidbefore step d, or combined with said second fluid before step d, oradded in step d.

8. The method of any preceding or following embodiment/feature/aspect,wherein carbon black is present in said silica elastomer composite in anamount of from about 10 wt % to about 50 wt % based on totalparticulates present in said silica elastomer composite.9. The method of any preceding or following embodiment/feature/aspect,wherein said flow of said solid or semi-solid silica-containingcontinuous rubber phase forms in two seconds or less after combiningsaid first fluid flow and second fluid flow.10. The method of any preceding or following embodiment/feature/aspect,wherein said flow of said solid or semi-solid silica-containingcontinuous rubber phase forms in about 50 milliseconds to about 1500milliseconds after combining said first fluid flow and second fluidflow.11. The method of any preceding or following embodiment/feature/aspect,wherein said first fluid in step (a) further comprises at least onesalt.12. The method of any preceding or following embodiment/feature/aspect,wherein said first fluid in step (a) further comprises at least oneacid.13. The method of any preceding or following embodiment/feature/aspect,wherein said solid or semi-solid silica-containing continuous rubberphase comprises from about 40 wt % to about 95 wt % water or aqueousfluid.14. The method of any preceding or following embodiment/feature/aspect,wherein said combining occurs in a reaction zone having a volume ofabout 10 cc to about 500 cc.15. The method of any preceding or following embodiment/feature/aspect,where the relative volumetric flows are at a volumetric flow ratio offirst fluid to second fluid of from 0.4:1 to 3.2:1.16. The method of any preceding or following embodiment/feature/aspect,where the relative volumetric flows are at a volumetric flow ratio offirst fluid to second fluid of from 0.2:1 to 2.8:1.17. The method of any preceding or following embodiment/feature/aspect,wherein the relative volumetric flows are at a volumetric flow ratio offirst fluid to second fluid of from 0.4:1 to 3.2:1, and saiddestabilized dispersion of silica includes at least one salt.18. The method of any preceding or following embodiment/feature/aspect,wherein the relative volumetric flows are at a volumetric flow ratio offirst fluid to second fluid of from 0.2:1 to 2.8:1, and saiddestabilized dispersion of silica includes at least one acid.19. The method of any preceding or following embodiment/feature/aspect,wherein said elastomer latex comprises a base, said destabilizeddispersion of silica comprises at least one acid, and a molar ratio ofhydrogen ions in said acid in said first fluid to said base in saidsecond fluid is from 1 to 4.5.20. The method of any preceding or following embodiment/feature/aspect,wherein said destabilized dispersion of silica comprises at least oneacid, and wherein said elastomer latex present in said second fluid hasan ammonia concentration of from about 0.3 wt % to about 0.7 wt % basedon the weight of the elastomer latex, and a molar ratio of hydrogen ionsin said acid in said first fluid to ammonia in said second fluid is atleast 1:1.21. The method of any preceding or following embodiment/feature/aspect,wherein said silica content of said silica elastomer composite is fromabout 26 phr to about 80 phr.22. The method of any preceding or following embodiment/feature/aspect,wherein said silica content of said silica elastomer composite is fromabout 40 phr to about 115 phr.23. The method of any preceding or following embodiment/feature/aspect,wherein said destabilized dispersion of silica comprises about 6 wt % toabout 35 wt % silica.24. The method of any preceding or following embodiment/feature/aspect,wherein said destabilized dispersion of silica comprises about 10 wt %to about 28 wt % silica.25. The method of any preceding or following embodiment/feature/aspect,further comprising recovering said solid or semi-solid silica-containingcontinuous rubber phase at ambient pressure.26. The method of any preceding or following embodiment/feature/aspect,wherein said first fluid comprising said destabilized dispersion ofsilica has a zeta potential magnitude of less than 30 mV.27. The method of any preceding or following embodiment/feature/aspect,wherein said destabilized dispersion of silica includes at least onesalt, wherein salt ion concentration in said destabilized dispersion isfrom about 10 mM to about 160 mM.28. The method of any preceding or following embodiment/feature/aspect,wherein said destabilized dispersion of silica includes at least onesalt, wherein said salt is present in said destabilized dispersion in anamount of from about 0.2 wt % to about 2 wt % based on weight of saiddestabilized dispersion.29. The method of any preceding or following embodiment/feature/aspect,wherein said destabilized dispersion of silica includes at least oneacid, wherein said acid is present in said destabilized dispersion in anamount of from about 0.8 wt % to about 7.5 wt % based on weight of saiddestabilized dispersion.30. The method of any preceding or following embodiment/feature/aspect,wherein said destabilized dispersion of silica includes at least oneacid, wherein acid concentration in said destabilized dispersion is fromabout 200 mM to about 1000 mM.31. The method of any preceding or following embodiment/feature/aspect,wherein step (c) is carried out with the continuous flow of the firstfluid at a velocity A and the continuous flow of the second fluid at avelocity B, and velocity A is at least 2 times faster than velocity B.32. The method of any preceding or following embodiment/feature/aspect,wherein step (c) is carried out in a semi-confined reaction zone and thefirst fluid has a velocity sufficient to induce cavitation in thereaction zone upon combining with the second fluid.33. The method of any preceding or following embodiment/feature/aspect,wherein the second fluid has a velocity sufficient to create turbulentflow.34. The method of any preceding or following embodiment/feature/aspect,wherein said dispersion of silica comprises a surface-modified silicahaving hydrophobic surface moieties.35. The method of any preceding or following embodiment/feature/aspect,wherein said first fluid comprises an aqueous fluid.36. The method of any preceding or following embodiment/feature/aspect,wherein said first fluid comprises an aqueous fluid and about 6 wt % toabout 31 wt % silica and at least 3 wt % carbon black.37. The method of any preceding or following embodiment/feature/aspect,wherein said first fluid comprises an aqueous fluid, further comprisingat least one salt, and at least one acid.38. The method of any preceding or following embodiment/feature/aspect,said method further comprising destabilizing a dispersion of silica bylowering a pH of the dispersion of silica so as to form the destabilizeddispersion of silica provided in step (a).39. The method of any preceding or following embodiment/feature/aspect,said method further comprising destabilizing a dispersion of silica bylowering a pH of the dispersion of silica to a pH of from 2 to 4 so asto form the destabilized dispersion of silica provided in step (a).40. The method of any preceding or following embodiment/feature/aspect,wherein said silica has a hydrophilic surface.41. The method of any preceding or following embodiment/feature/aspect,wherein said silica is a highly dispersible silica (HDS).42. The method of any preceding or following embodiment/feature/aspect,wherein said acid comprises acetic acid, formic acid, citric acid,phosphoric acid, or sulfuric acid, or any combinations thereof.43. The method of any preceding or following embodiment/feature/aspect,wherein said acid has a molecular weight or an average molecular weightbelow 200.44. The method of any preceding or following embodiment/feature/aspect,wherein said salt comprises at least one Group 1, 2, or 13 metal salt.45. The method of any preceding or following embodiment/feature/aspect,wherein said salt comprises a calcium salt, magnesium salt, or aluminumsalt, or a combination thereof.46. The method of any preceding or following embodiment/feature/aspect,said method further comprising subjecting silica to mechanicalprocessing to reduce particle agglomeration, and/or adjust particle sizedistribution.47. The method of any preceding or following embodiment/feature/aspect,wherein the silica is precipitated silica or fumed silica or colloidalsilica, or any combinations thereof.48. The method of any preceding or following embodiment/feature/aspect,wherein said silica has a BET surface area of from about 20 m²/g toabout 450 m²/g.49. The method of any preceding or following embodiment/feature/aspect,wherein said elastomer latex is natural rubber latex.50. The method of any preceding or following embodiment/feature/aspect,wherein said the natural rubber latex is in the form of a field latex,latex concentrate, desludged latex, chemically modified latex,enzymatically modified latex, or any combinations thereof.51. The method of any preceding or following embodiment/feature/aspect,wherein said the natural rubber latex is in the form of an epoxidizednatural rubber latex.52. The method of any preceding or following embodiment/feature/aspect,wherein said the natural rubber latex is in the form of a latexconcentrate.53. The method of any preceding or following embodiment/feature/aspect,further comprising mixing the silica elastomer composite with additionalelastomer to form an elastomer composite blend.54. A method for making a rubber compound comprising

(a) conducting the method of any preceding or followingembodiment/feature/aspect, and

(b) blending the silica elastomer composite with other components toform the rubber compound, wherein said other components comprise atleast one antioxidant, sulfur, polymer other than an elastomer latex,catalyst, extender oil, resin, coupling agent, additional elastomercomposite(s), or reinforcing filler, or any combinations thereof.

55. A method for making a rubber article selected from tires, moldings,mounts, liners, conveyors, seals, or jackets, comprising

(a) conducting the method of any preceding or followingembodiment/feature/aspect, and

(b) compounding the silica elastomer composite with other components toform a compound, and

(c) vulcanizing the compound to form said rubber article.

56. The method of any preceding or following embodiment/feature/aspect,further comprising conducting one or more post processing steps afterrecovering the silica elastomer composite.

57. The method of any preceding or following embodiment/feature/aspect,wherein the post processing steps comprise at least one of:

a) dewatering the silica elastomer composite to obtain a dewateredmixture;

b) mixing or compounding the dewatered mixture to obtain a compoundedsilica elastomer composite;

c) milling the compounded silica elastomer composite to obtain a milledsilica elastomer composite;

d) granulating or mixing the milled silica elastomer composite;

e) baling the silica elastomer composite after the granulating or mixingto obtain a baled silica elastomer composite;

f) extruding the silica elastomer composite;

g) calendaring the silica elastomer composite; and/or

h) optionally breaking apart the baled silica elastomer composite andmixing with further components.

58. The method of any preceding or following embodiment/feature/aspect,wherein the post processing steps comprise at least roll milling of thesilica elastomer composite.

59. The method of any preceding or following embodiment/feature/aspect,wherein the post processing steps comprise compressing the solid orsemi-solid silica-containing continuous rubber phase to remove fromabout 1 wt % to about 15 wt % of aqueous fluid contained therein.60. The method of any preceding or following embodiment/feature/aspect,wherein the elastomer latex is brought into contact with at least onedestabilizing agent as the destabilized dispersion of silica is combinedwith the elastomer latex.61. The method of any preceding or following embodiment/feature/aspect,further comprising bringing the flow of solid or semi-solidsilica-containing continuous rubber phase into contact with at least onedestabilizing agent.62. The method of any preceding or following embodiment/feature/aspect,further comprising the step of conducting one or more of the followingwith the solid or semi-solid silica-containing continuous rubber phase:

a) transferring the solid or semi-solid silica-containing continuousrubber phase to a holding tank or container;

b) heating the solid or semi-solid silica-containing continuous rubberphase to reduce water content;

c) subjecting the solid or semi-solid silica-containing continuousrubber phase to an acid bath;

d) mechanically working the solid or semi-solid silica-containingcontinuous rubber phase to reduce water content.

63. The method of any preceding or following embodiment/feature/aspect,wherein said silica elastomer composite is a semi-solidsilica-containing continuous rubber phase, and said method furthercomprising converting said semi-solid silica-containing continuousrubber phase to a solid silica-containing continuous rubber phase.64. The method of any preceding or following embodiment/feature/aspect,wherein said semi-solid silica-containing continuous rubber phase isconverted to said solid silica-containing continuous rubber phase bytreatment with an aqueous fluid comprising at least one acid, or atleast one salt, or a combination of at least one acid and at least onesalt.65. The method of any preceding or following embodiment/feature/aspect,wherein said second fluid comprises a blend of two or more differentelastomer latices.66. The method of any preceding or following embodiment/feature/aspect,wherein said process further comprises providing one or more additionalfluids and combining the one or more additional fluids with said firstfluid flow and second fluid flow, wherein said one or more additionalfluids comprise one or more elastomer latex fluids, and said additionalfluids are the same as or different from said elastomer latex present insaid second fluid flow.67. The method of any preceding or following embodiment/feature/aspect,wherein said silica content of said silica elastomer composite is fromabout 26 phr to about 180 phr.68. A solid silica and carbon black-containing continuous rubber phasearticle comprising at least 25 parts per hundred of rubber (phr) ofsilica dispersed in natural rubber and at least 40 wt % aqueous fluid,and having a length dimension (L), wherein the solid silica-containingcontinuous rubber phase article can be stretched to at least 130-150% of(L) without breaking.69. The solid silica and carbon black-containing continuous rubber phasearticle of any preceding or following embodiment/feature/aspect, furthercomprising at least 10 phr of carbon black dispersed in said naturalrubber.

The present invention can include any combination of these variousfeatures or embodiments above and/or below as set forth in any sentencesand/or paragraphs herein. Any combination of disclosed features hereinis considered part of the present invention and no limitation isintended with respect to combinable features.

Applicants specifically incorporate the entire contents of all citedreferences in this disclosure. Further, when an amount, concentration,or other value or parameter is given as either a range, preferred range,or a list of upper preferable values and lower preferable values, thisis to be understood as specifically disclosing all ranges formed fromany pair of any upper range limit or preferred value and any lower rangelimit or preferred value, regardless of whether ranges are separatelydisclosed. Where a range of numerical values is recited herein, unlessotherwise stated, the range is intended to include the endpointsthereof, and all integers and fractions within the range. It is notintended that the scope of the invention be limited to the specificvalues recited when defining a range.

Other embodiments of the present invention will be apparent to thoseskilled in the art from consideration of the present specification andpractice of the present invention disclosed herein. It is intended thatthe present specification and examples be considered as exemplary onlywith a true scope and spirit of the invention being indicated by thefollowing claims and equivalents thereof.

What is claimed is:
 1. A method of producing a silica elastomercomposite, comprising: (a) providing a continuous flow under pressure ofat least one first fluid containing dispersed particles and comprising adestabilized dispersion of silica, and a continuous flow of at least asecond fluid comprising elastomer latex; (b) providing volumetric flowof the first fluid relative to that of the second fluid to yield asilica content of about 15 phr to about 180 phr in the silica elastomercomposite; (c) combining the first fluid flow and the second fluid flowwith a sufficiently energetic impact to distribute the silica within theelastomer latex to obtain a flow of a solid silica-containing continuousrubber phase or semi-solid silica-containing continuous rubber phase;and (d) recovering said solid or semi-solid silica-containing continuousrubber phase that is the silica elastomer composite, wherein said atleast one first fluid is provided as: i) two streams with one streamcomprising a dispersion of the dispersed particles comprising carbonblack and the other stream comprising the destabilized dispersion ofsilica; or ii) a single stream comprising a dispersion of the dispersedparticles comprising carbon black and the destabilized dispersion ofsilica; or iii) a single stream of the destabilized dispersion of silicathat includes carbon black, further comprising, subjecting one or more,said dispersion(s) to at least one mechanical processing step, whereinsaid mechanical processing step comprises grinding, milling,comminution, bashing, or high shear fluid processing, or anycombinations thereof.
 2. The method of claim 1, wherein said mechanicalprocessing step comprises grinding said dispersion(s) one or more times.3. The method of claim 1, wherein said mechanical processing stepreduces particle agglomeration, and/or adjusts particle sizedistribution.
 4. The method of claim 1, wherein said flow of said solidor semi-solid silica-containing continuous rubber phase forms in twoseconds or less after combining said first fluid flow and second fluidflow.
 5. The method of claim 1, wherein said flow of said solid orsemi-solid silica-containing continuous rubber phase forms in about 50milliseconds to about 1500 milliseconds after combining said first fluidflow and second fluid flow.
 6. The method of claim 1, wherein saidcombining occurs in a reaction zone having a volume of about 10 cc toabout 500 cc.
 7. The method of claim 1, wherein the volumetric flow ofsaid first fluid and of said second fluid are at a volumetric flow ratioof first fluid to second fluid of from 0.2:1 to 2.8:1.
 8. The method ofclaim 1, wherein the volumetric flow of said first fluid and of saidsecond fluid are at a volumetric flow ratio of first fluid to secondfluid of from 0.4:1 to 3.2:1, and said destabilized dispersion of silicaincludes at least one salt.
 9. The method of claim 1, wherein thevolumetric flow of said first fluid and of said second fluid are at avolumetric flow ratio of first fluid to second fluid of from 0.2:1 to2.8:1, and said destabilized dispersion of silica includes at least oneacid.
 10. The method of claim 1, wherein said destabilized dispersion ofsilica comprises at least one acid, and wherein said elastomer latexpresent in said second fluid has an ammonia concentration of from about0.3 wt % to about 0.7 wt % based on the weight of the elastomer latex,and a molar ratio of hydrogen ions in said acid in said first fluid toammonia in said second fluid is at least 1:1.
 11. The method of claim 1,wherein said silica content of said silica elastomer composite is fromabout 26 phr to about 80 phr.
 12. The method of claim 1, wherein saidsilica content of said silica elastomer composite is from about 40 phrto about 115 phr.
 13. The method of claim 1, wherein said destabilizeddispersion of silica comprises about 10 wt % to about 28 wt % silica.14. The method of claim 1, wherein said destabilized dispersion ofsilica includes at least one salt, wherein said salt is present in saiddestabilized dispersion in an amount of from about 0.2 wt % to about 2wt % based on weight of said destabilized dispersion.
 15. The method ofclaim 1, wherein said destabilized dispersion of silica includes atleast one acid, wherein said acid is present in said destabilizeddispersion in an amount of from about 0.8 wt % to about 7.5 wt % basedon weight of said destabilized dispersion.
 16. The method of claim 1,wherein said first fluid is an aqueous fluid.
 17. The method of claim 1,wherein said first fluid is an aqueous fluid, further comprising atleast one salt, and at least one acid.
 18. The method of claim 1,wherein said first fluid in step (a) further comprises at least oneacid, and, wherein said acid has a molecular weight or an averagemolecular weight below
 200. 19. The method of claim 1, said methodfurther comprising subjecting silica to mechanical processing to reduceparticle agglomeration, and/or adjust particle size distribution. 20.The method of claim 1, wherein the silica is precipitated silica orfumed silica or colloidal silica, or any combinations thereof.
 21. Themethod of claim 1, wherein said silica has a BET surface area of fromabout 20 m²/g to about 450 m²/g.
 22. The method of claim 1, wherein saidelastomer latex is natural rubber latex.
 23. The method of claim 22,wherein the natural rubber latex is in the form of an epoxidized naturalrubber latex.
 24. The method of claim 22, wherein the natural rubberlatex is in the form of a latex concentrate.
 25. The method of claim 1,further comprising conducting one or more post processing steps afterrecovering the silica elastomer composite, wherein the post processingsteps comprise at least roll milling of the silica elastomer composite.26. The method of claim 1, further comprising conducting one or morepost processing steps after recovering the silica elastomer composite,wherein the post processing steps comprise compressing the solid orsemi-solid silica-containing continuous rubber phase to remove fromabout 1 wt % to about 15 wt % of aqueous fluid contained therein. 27.The method of claim 1, further comprising bringing the flow of solid orsemi-solid silica-containing continuous rubber phase into contact withat least one destabilizing agent.
 28. The method of claim 1, whereinsaid second fluid comprises a blend of two or more different elastomerlatices.
 29. The method of claim 1, further comprising providing one ormore additional fluids and combining the one or more additional fluidswith said first fluid flow and second fluid flow, wherein said one ormore additional fluids comprise one or more elastomer latex fluids, andsaid additional fluids are the same as or different from said elastomerlatex present in said second fluid flow.